If you want to actually fully degoogle, you wouldn't want to use Revanced. Revanced just patches the official YouTube App.
I personally use NewPipe when watching on my phone, but I do have Revanced YouTube installed as well just for casting to my TV. Convenience for me.
That's because Feeder does their OPML file differently. Their OPML file includes Feeder settings. You have to wait for v0.9.13 release that makes it compatible. It'll be the next release. Current release is v0.9.12