As has been proven by other companies recently, so long as there is a "catchall" clause in the terms, anything you do has the potential to be against their terms.

All you can ever really do is hope to not be caught up in something Google (or its bots) considers "bad".

EDIT: A few catchall terms from YouTube's TOS:

"YouTube may, in its sole discretion, modify or revise these Terms of Service and policies at any time, and you agree to be bound by such modifications or revisions."

"You agree not to access Content through any technology or means other than the video playback pages of the Service itself, the Embeddable Player, or other explicitly authorized means YouTube may designate." (There go all New Pipe accounts)

"YouTube reserves the right to discontinue any aspect of the Service at any time."

"YouTube reserves the right to decide whether Content violates these Terms of Service for reasons other than copyright infringement, [...]. YouTube may at any time, without prior notice and in its sole discretion, [...] terminate a user's account for submitting such material in violation of these Terms of Service."

I find that to be a possibility too. If none of the other newpipe users in the thread got suspended for "using 3rd party app outside of Play Store to go around Youtube ads", chances are newpipe isn't on the app blacklist.

It might also be possible that someone was violating terms while imposting as the user in question using snooped access tokens or whatever. There won't be a trial where the reason might come to light.

Violating terms or not- it's still a lot of power for Google to hold over a person and there should be some consumer protections for this.

There is also no proof (screenshots/etc) that this user is actually suspended, and not just random trolling.

With so much tied to a Google account, there should be some means of dealing with it. With this person being in Finland, they should have some means of at least extracting all account data thanks to the GDPR or other protection laws.

Except that, if your account is cancelled, the datas are deleted (or should have been)... so there's nothing to download, even from a GDPR point of view.

So the probleme to be able to use that GDPR feature... is to still have an account