Hi! Since there is this thread summing up WebExtensions alternatives for legacy addons, I think it is a good idea to try to list the non-WebExtension alternatives we have since there are quite a few.
This will really help with supporting users on social media.
FireFTP - Filezilla or any FTP client. A lot of users don’t know unused addons still use resources and a separate app is actually better.
Tamper Data - OWASP ZAP or any pen testing proxy. Edit and resend in DevTools might cover some really small and basic use cases.
Tab Groups - Any tab grouping addon + userChrome.css hack to hide the tab strip
FT DeepDark - Builtin dark theme + userChrome.css and userContent.css hack
Tab MIx PLus - The multi-row feature can be covered with userChrome.css.
Classic Theme Restorer - this repo and this issue
Roomy Bookmarks Toolbar - userChrome.css
Beyond Australis - userChrome.css
BookmarksDropDown - userChrome.css
More useful tweaks here https://github.com/Timvde/UserChrome-Tweaks and here https://vimeo.com/235050016
Please contribute your own ideas