Just to clarify: you don’t need a phone number for proton, and you can use a burner email as your backup. I agree with you though, I’d prefer not to give either, put back at the emails are standard, so there is someplace to send a recovery code.
The controversy is that the code is not fully open source, but it was originally labeled as FOSS.
I use a front end called Grayjay. You can log in with your YouTube account in the settings and transfer everything over, or you can set up a Polycentric account and never use YouTube directly at all. It’s ad-free on my device and I notice that it even shows locked Patreon content on some channels.
I downloaded it directly from their website and use F-Droid as the repository. I was able to do all this on an Android tablet, so it’s fairly simple.
Whatsapp tells me every day it’s unable to back up my data, and begs me to remedy the issue. Lol, nope!