Whatsapp tells me every day it's unable to back up my data, and begs me to remedy the issue. Lol, nope!

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.