I can only add my own anecdotal experience for whatever that is worth. I do not have a Google or Youtube account and have not been experiencing this. I do not use a VPN and I do use NoScript+uBlock and some hardening options for Firefox. The only time they have required a login from me was for a video flagged "adult" but I get around that with yt-dlp. They have never blocked my use of yt-dlp from my home IP same static IP for years.

They did however block me using yt-dlp from a VPS provider. Bandwidth exceeded despite my having that IP for years so I assume they now aggregate VPS providers IP addresses by CIDR or AS number. Perhaps they are aggregating iCloud Private Relays by CIDR or AS number as well?

YouTube is really a crappy platform. I wish it were a government service and outside public hands. It might not be as good but I'd glady accept no 8K, no algorithm, slower streaming in exchange for it not being in Google's hands.

There needs to be a YouTube alternative that is run by a nonprofit.

Oh yeah, I would love that.

Works fine for me (no account, from the US, using FireFox w/NoScript to block most JS).

Google is plausibly under pressure from their large advertisers - who do not want to pay Google mucho $millions, only for their messages to be shown to bots, or to ineligible audiences, or hidden by alternative frontends, or whatever. But due to the "don't mention the elephant" social conventions about advertising, Google can't actually say that in its error message.

YouTube is Google, never forget that..

Google want to track you everywhere.. and sell that data to advertisers and their 3rd party partners who pay hundreds of millions for your data..

NEVER EVER LOGIN !!! buy a DVD & VHS player if you need content, get offline, find better places than YouTube..

Do you mean just refusing to play some age-restricted video? That happened not recently.

No, that is not what I mean. That message is different, it tells you to sign in to confirm your age, and has been there for years.

I think YT may be nearing its EOL. Save what matters to you.

It's the "panic" effect from all things google when AI is taking the bread from search relevance..

Not may, but does

Can confirm this is affecting alternative frontends.