You can use Yattee. There’s a guide on how to set it up correctly. You can also just add the Piped website to your homescreen. That’s what I’ve been doing for over a year, before I switched to GrapheneOS. Now I can enjoy LibreTube.
The recommendations on Piped (privacy-focused YouTube front-end) are fine for me. I actually prefer it when the suggestions are related to the video I am watching right now, than when they are related to some random video I watched 2 weeks ago and I have no interest in.
Entirely. On GrapheneOS, Google Play services run in the normal Android app sandbox, just like any other app you install. That way, they only have the permissions you granted them using the permission manager. GrapheneOS doesn’t grant any extra privileges, and you can remove the Play services app at any time. Read more at grapheneos.org/features#sandboxed-google-play