Google started using IP range blocks recently. If they decide that your IP stinks, they'll block YouTube viewing and demand that you log in.

It's inconsistent as fuck, and even TOR exit nodes still work without a log in sometimes.

I can confirm this. I guess they didn't like me using Invidious.

That's bad enough for normal VPN users who use VPN for privacy reasons. But a lot of countries have heavily censored web, and not using a VPN is simply not an option there.

Good on Google for kicking people while they're down.

I think for me it has been this way for a year or so. Maybe it is because I am on a VPN. I also cannot view YouTube videos on YouTube any longer, because it always wants me to log in, to "prove I am not a bot". So I have switched to only using invidious instances, and if they don't work, then I just cannot watch the video.

I wish content creators would think of their own good more, and start publishing on multiple platforms. Are there any terms that YouTube has for them, that reduce revenue, if they publish elsewhere as well? Or is it mostly just them being unaware?

It's a VPN thing, or a 'you've been downloading too much and are ratelimiting you' thing.