Classic Theme Restorer se loučí:

This add-on will stop working when Firefox 57 arrives in November 2017 and Mozilla drops support for XUL / XPCOM / legacy add-ons. It should still work on Firefox 52 ESR until ESR moves to Firefox 59 ESR in 2018 (~Q2).

There is no "please port it" or "please add support for it" this time, because the entire add-on eco system changes and the technology behind this kind of add-on gets dropped without replacement.