Bootstrap 4's margin/padding classes. Bootstrap changed their margin/padding right + left classes to start + end, this adds the old ones back to your SCSS file. Be sure to tree-shake!

bootstrap-5-spacing-shiv.scss

// Notes
// * If adding alongside Bootstrap 5's margin/padding classes, you'll have to remove some stuff from this file so that there's not duplicate definitions.
//   * Check the comments for details
// * XXL sizing was not included in Bootstrap 4, but added here for compatibility

////// remove the following variables if bootstrap is included in your SCSS //////////
$grid-breakpoints: (
  xs: 0,
  sm: 576px,
  md: 768px,
  lg: 992px,
  xl: 1200px,
  xxl: 1400px
) !default;
$spacer: 1rem !default;
$spacers: (
  0: 0,
  1: $spacer * .25,
  2: $spacer * .5,
  3: $spacer,
  4: $spacer * 1.5,
  5: $spacer * 3,
) !default;
/////////////////////////


// margin and padding definition; if you're adding directly to Bootstrap 5, remove everything except `pr`, `pl`, `mr`, and `ml`
$space-prefixes: (p : padding, pt : padding-top, pr : padding-right, pb : padding-bottom, pl : padding-left, m : margin, mt : margin-top, mr : margin-right, mb : margin-bottom, ml : margin-left) !default;

@each $breakpoint-name, $breakpoint-value in $grid-breakpoints {
    // don't use media queries if regular (ex. `pr-5`)
    @if ($breakpoint-value == 0) {
        @each $attr-short, $attr-long in $space-prefixes {
            @each $name, $value in $spacers {
                .#{$attr-short}-#{$name} {
                    #{$attr-long}: #{$value} !important;
                }
            }
      
            .#{$attr-short}-auto {
                #{$attr-long}: auto !important;
            }
        }
    }
    @else {
        @media screen and (min-width: $breakpoint-value) {
            @each $attr-short, $attr-long in $space-prefixes {
                @each $name, $value in $spacers {
                    .#{$attr-short}-#{$breakpoint-name}-#{$name} {
                        #{$attr-long}: #{$value} !important;
                    }
                }
      
                .#{$attr-short}-#{$breakpoint-name}-auto {
                    #{$attr-long}: auto !important;
                }
            }
        }
    }
}