diff --git a/theme/boost/scss/moodle/blocks.scss b/theme/boost/scss/moodle/blocks.scss
index 8f730f59b52..27f3881cfa7 100644
--- a/theme/boost/scss/moodle/blocks.scss
+++ b/theme/boost/scss/moodle/blocks.scss
@@ -144,10 +144,6 @@ $card-gutter : $card-deck-margin * 2;
         width: 36px;
         padding: 0;
         border-radius: 50%;
-
-        @include hover-focus {
-            background-color: $gray-200;
-        }
     }
 }
 
@@ -268,7 +264,8 @@ $card-gutter : $card-deck-margin * 2;
     }
 
     a.dashboard-card {
-        @include hover-focus {
+        &:hover,
+        &:focus {
             text-decoration: none;
             h6 {
                 text-decoration: underline;
diff --git a/theme/boost/scss/moodle/buttons.scss b/theme/boost/scss/moodle/buttons.scss
index c03e10c98f5..b6b62e3e6f8 100644
--- a/theme/boost/scss/moodle/buttons.scss
+++ b/theme/boost/scss/moodle/buttons.scss
@@ -47,7 +47,8 @@ p.arrow_button {
     border-radius: 50%;
     flex-shrink: 0;
 
-    @include hover-focus {
+    &:hover,
+    &:focus {
         background-color: $gray-200;
     }
 
diff --git a/theme/boost/scss/moodle/core.scss b/theme/boost/scss/moodle/core.scss
index 1361235f0d2..5ec22406c89 100644
--- a/theme/boost/scss/moodle/core.scss
+++ b/theme/boost/scss/moodle/core.scss
@@ -2579,11 +2579,6 @@ $picker-emojis-per-row: 7 !default;
             line-height: $picker-emoji-button-size;
             font-size: $picker-emoji-button-font-size;
             overflow: hidden;
-
-            @include hover-focus {
-                color: inherit;
-                text-decoration: none;
-            }
         }
     }
 
@@ -2900,7 +2895,8 @@ body.dragging {
 .collapse-list {
     .collapse-list-item {
         padding: $collapse-list-item-padding-y $collapse-list-item-padding-x;
-        @include hover-focus() {
+        &:hover,
+        &:focus {
             background-color: $collapse-list-item-hover-bg;
             border-color: $collapse-list-item-hover-border;
         }
diff --git a/theme/boost/scss/moodle/courseindex.scss b/theme/boost/scss/moodle/courseindex.scss
index f640ccc56f6..a97f0d39607 100644
--- a/theme/boost/scss/moodle/courseindex.scss
+++ b/theme/boost/scss/moodle/courseindex.scss
@@ -13,7 +13,8 @@ $courseindex-item-radius: $border-radius !default;
 $courseindex-item-current: $primary !default;
 
 @mixin courseindex-item-hover() {
-    @include hover-focus() {
+    &:hover,
+    &:focus {
         color: $courseindex-link-hover-color;
 
         .courseindex-link,
@@ -60,7 +61,8 @@ $courseindex-item-current: $primary !default;
         .courseindex-link,
         .courseindex-chevron {
             color: $courseindex-link-color;
-            @include hover-focus() {
+            &:hover,
+            &:focus {
                 color: $courseindex-link-hover-color;
                 text-decoration: none;
             }
@@ -112,8 +114,8 @@ $courseindex-item-current: $primary !default;
             a {
                 color: $courseindex-link-color-selected;
             }
-
-            @include hover-focus() {
+            &:hover,
+            &:focus {
                 background-color: darken($courseindex-item-page-bg, 7.5%);
                 color: darken($courseindex-link-color-selected, 10%);
                 .courseindex-link,
diff --git a/theme/boost/scss/moodle/message.scss b/theme/boost/scss/moodle/message.scss
index 9ae0cb31d7f..fedc74e3e84 100644
--- a/theme/boost/scss/moodle/message.scss
+++ b/theme/boost/scss/moodle/message.scss
@@ -507,10 +507,6 @@ $message-day-color: color-yiq($message-app-bg) !default;
         border-radius: 50%;
         flex-shrink: 0;
 
-        @include hover-focus {
-            background-color: $gray-200;
-        }
-
         @each $size, $length in $iconsizes {
             &.icon-size-#{$size} {
                 height: ($length + 20px) !important; /* stylelint-disable-line declaration-no-important */
diff --git a/theme/boost/scss/moodle/modal.scss b/theme/boost/scss/moodle/modal.scss
index 23ebb8db601..8924d8495e7 100644
--- a/theme/boost/scss/moodle/modal.scss
+++ b/theme/boost/scss/moodle/modal.scss
@@ -23,7 +23,8 @@
 
         // Inherit the opacity when focus is received for better focus outline contrast.
         &:not(:disabled):not(.disabled) {
-            @include hover-focus() {
+            &:hover,
+            &:focus {
                 opacity: inherit;
             }
         }
diff --git a/theme/boost/scss/moodle/moremenu.scss b/theme/boost/scss/moodle/moremenu.scss
index 3c41bacb83f..3f47c7d5e86 100644
--- a/theme/boost/scss/moodle/moremenu.scss
+++ b/theme/boost/scss/moodle/moremenu.scss
@@ -12,7 +12,8 @@
         border-bottom: solid 3px transparent;
         border-left: none;
         border-top: none;
-        @include hover-focus() {
+        &:hover,
+        &:focus {
             @include hover-navbar();
         }
 
@@ -76,7 +77,8 @@
             }
             .dropdown-item {
                 background-color: $gray-100;
-                @include hover-focus() {
+                &:hover,
+                &:focus {
                     color: $dropdown-link-hover-color;
                     @include gradient-bg($dropdown-link-active-bg);
                 }
diff --git a/theme/boost/scss/moodle/tables.scss b/theme/boost/scss/moodle/tables.scss
index d4e2233bf53..92958d6a946 100644
--- a/theme/boost/scss/moodle/tables.scss
+++ b/theme/boost/scss/moodle/tables.scss
@@ -41,7 +41,7 @@
         }
     }
     tbody tr {
-        @include hover {
+        &:hover {
             color: $table-hover-color;
             background-color: $table-hover-bg;
             &.dimmed_text {
diff --git a/theme/boost/scss/moodle/undo.scss b/theme/boost/scss/moodle/undo.scss
index a6bfa397435..0cb23fbb6ba 100644
--- a/theme/boost/scss/moodle/undo.scss
+++ b/theme/boost/scss/moodle/undo.scss
@@ -134,7 +134,9 @@ body:not(.jsenabled) .langmenu:hover > .dropdown-menu,
 // Dont allow z-index creep anywhere.
 .page-item {
     &.active .page-link {
-        @include plain-hover-focus {
+        &,
+        &:hover,
+        &:focus {
             z-index: inherit;
         }
     }
diff --git a/theme/boost/scss/preset/default.scss b/theme/boost/scss/preset/default.scss
index 9368510df2c..a4ca46558c5 100644
--- a/theme/boost/scss/preset/default.scss
+++ b/theme/boost/scss/preset/default.scss
@@ -149,5 +149,3 @@ body {
 .btn-outline-warning {
     @include button-outline-variant($warning-outline);
 }
-
-@include bg-variant(".bg-gray", $gray-200, true);
diff --git a/theme/boost/style/moodle.css b/theme/boost/style/moodle.css
index 06cbfe8dccf..0ea6e489bcb 100644
--- a/theme/boost/style/moodle.css
+++ b/theme/boost/style/moodle.css
@@ -25449,10 +25449,6 @@ input[disabled] {
   font-size: 24px;
   overflow: hidden;
 }
-.emoji-picker .picker-row .emoji-button:hover, .emoji-picker .picker-row .emoji-button:focus {
-  color: inherit;
-  text-decoration: none;
-}
 .emoji-picker .emoji-preview {
   height: 40px;
   font-size: 40px;
@@ -27000,9 +26996,6 @@ body.behat-site .action-menu .dropdown-subpanel-content.show {
   padding: 0;
   border-radius: 50%;
 }
-.block .block-cards .btn.btn-link.btn-icon:hover, .block .block-cards .btn.btn-link.btn-icon:focus {
-  background-color: #e9ecef;
-}
 
 .dashboard-card-deck.one-row {
   flex-flow: nowrap;
@@ -31603,9 +31596,6 @@ a.ygtvspacer:hover {
   border-radius: 50%;
   flex-shrink: 0;
 }
-.message-app .btn.btn-link.btn-icon:hover, .message-app .btn.btn-link.btn-icon:focus {
-  background-color: #e9ecef;
-}
 .message-app .btn.btn-link.btn-icon.icon-size-0 {
   height: 20px !important; /* stylelint-disable-line declaration-no-important */
   width: 20px !important; /* stylelint-disable-line declaration-no-important */
@@ -38814,14 +38804,4 @@ body {
 }
 .btn-outline-warning:not(:disabled):not(.disabled):active:focus, .btn-outline-warning:not(:disabled):not(.disabled).active:focus, .show > .btn-outline-warning.dropdown-toggle:focus {
   box-shadow: 0 0 0 0.2rem rgba(166, 103, 14, 0.5);
-}
-
-.bg-gray {
-  background-color: #e9ecef !important;
-}
-
-a.bg-gray:hover, a.bg-gray:focus,
-button.bg-gray:hover,
-button.bg-gray:focus {
-  background-color: #cbd3da !important;
 }
\ No newline at end of file
diff --git a/theme/boost/upgrade.txt b/theme/boost/upgrade.txt
index ca3f8893fe7..18ac799f504 100644
--- a/theme/boost/upgrade.txt
+++ b/theme/boost/upgrade.txt
@@ -5,6 +5,18 @@ information provided here is intended especially for theme designers.
 * Bootstrap badge color helper clases (badge-[primary|secondary|...]) are no longer used, use bg-[primary|secondary|...] instead.
 * Bootstrap badge-pill is no longer used, use rounded-pill instead.
 * The bootstrap ´.media´ helper class has been replaced with utility classes (´d-flex´, ´flex-shrink-´, ´flex-grow-´, ...)
+* The following bootstrap mixins that will be deprecated in BS5 have been replaced with their CSS code:
+  - hover, hover-focus, plain-hover-focus and hover-focus-active
+  - float-left, float-right and float-none
+  - nav-divider
+  - img-retina
+  - text-hide
+  - invisible
+  - form-control-focus
+  - text-emphasis-variant
+  - size
+  - make-container-max-widths
+  - g-variant and bg-gradient-variant
 
 === 4.3 ===
 * The $activity-iconcontainer-height and $activity-iconcontainer-width variables have been changed from 50px to 52px.
diff --git a/theme/classic/scss/classic/navbar-dark.scss b/theme/classic/scss/classic/navbar-dark.scss
index 2cfb9798a0a..3270bb80bb3 100644
--- a/theme/classic/scss/classic/navbar-dark.scss
+++ b/theme/classic/scss/classic/navbar-dark.scss
@@ -13,7 +13,8 @@ $nabvar-bg-color: $dark !default;
     a.dropdown-toggle,
     a .usertext {
         color: $navbar-dark-active-color;
-        @include hover-focus {
+        &:hover,
+        &:focus {
             color: $navbar-dark-hover-color;
         }
 
@@ -24,4 +25,4 @@ $nabvar-bg-color: $dark !default;
     .dropdown-menu a .icon {
         color: inherit !important; // stylelint-disable-line declaration-no-important
     }
-}
\ No newline at end of file
+}
diff --git a/theme/classic/style/moodle.css b/theme/classic/style/moodle.css
index d6adb76f1e5..38d4e67f341 100644
--- a/theme/classic/style/moodle.css
+++ b/theme/classic/style/moodle.css
@@ -25449,10 +25449,6 @@ input[disabled] {
   font-size: 24px;
   overflow: hidden;
 }
-.emoji-picker .picker-row .emoji-button:hover, .emoji-picker .picker-row .emoji-button:focus {
-  color: inherit;
-  text-decoration: none;
-}
 .emoji-picker .emoji-preview {
   height: 40px;
   font-size: 40px;
@@ -27000,9 +26996,6 @@ body.behat-site .action-menu .dropdown-subpanel-content.show {
   padding: 0;
   border-radius: 50%;
 }
-.block .block-cards .btn.btn-link.btn-icon:hover, .block .block-cards .btn.btn-link.btn-icon:focus {
-  background-color: #e9ecef;
-}
 
 .dashboard-card-deck.one-row {
   flex-flow: nowrap;
@@ -31603,9 +31596,6 @@ a.ygtvspacer:hover {
   border-radius: 50%;
   flex-shrink: 0;
 }
-.message-app .btn.btn-link.btn-icon:hover, .message-app .btn.btn-link.btn-icon:focus {
-  background-color: #e9ecef;
-}
 .message-app .btn.btn-link.btn-icon.icon-size-0 {
   height: 20px !important; /* stylelint-disable-line declaration-no-important */
   width: 20px !important; /* stylelint-disable-line declaration-no-important */