It will never be ported fully. It's one of those extensions that dived so deep into Firefox's source code that Mozilla changing things in the source code caused it to break a lot of the times.

Mozilla categorically doesn't want that anymore, as it will inevitably cause some Mozilla devs to try to not break those extensions and therefore not do things such as code refactoring. The sort of stuff that you can ignore in the short-term in order to not break extensions, but which causes huge problems in the long run.

The CTR dev has however created a userChrome.css file, which you can use to get at least the visual changes: http://techdows.com/2017/09/classic-theme-restorer-userchrom...

Dude, let it go already.