You need to uncomment the below code in the src/assets/scss/app.scss file.
@import "custom/rtl/general-rtl";
@import "custom/rtl/bootstrap-rtl";
@import "custom/rtl/spacing-rtl";
@import "custom/rtl/float-rtl";
@import "custom/rtl/text-rtl";
@import "custom/rtl/structure-rtl";
@import "custom/rtl/plugins-rtl";
@import "custom/rtl/components-rtl";
@import "custom/rtl/pages-rtl";