I wanted to make a frontend theme as clean and fast as possible, so wanted to remove all Drupal core stylsheets. After quite some research I couldn't find a complete solution, so scratched my own itch:
Here's is an example of how your_theme.info.yml could look like, to strip your frontend theme from all Drupal CSS -and JS files.
name: Your Theme
type: theme
description: "Your Theme description"
core_version_requirement: ^10
base theme: false
ckeditor_stylesheets:
- assets/css/editor/ck_editor.css
libraries:
- your_theme/global
regions:
main_menu: Main Menu
breadcrumbs: Breadcrumbs
content: Content
sidebar_right: Sidebar Right
footer_menu: Footer Menu
libraries-override:
core/jquery: your_theme/jquery-custom
system/base: false
views/views.module: false
core/internal.underscore: false
core/once: false
core/internal.backbone: false
core/drupalSettings: false
core/drupal: false
contextual/drupal.contextual-links: false
core/drupal.progress: false
core/drupal.active-link: false