I've been having some weird issues over the last few days with not being able to search for things in YouTube when I'm logged in via SmartTube account.
So I decided to try accessing it directly. Well guess what? It looks like YouTube now requires age verification in AU.
Sorry Google... I'm not uploading my passport, drivers licence or govt id to watch your shit. I am however now very incentivized to use Tube archivist and Jellyfin, plus cron job to scrape your shit with gleeful abandon.
EDIT: Rather than removed about it, I did something and made Smarttube work without a google account. If that floats your boat, have at it. It supports direct import of your saved playlists via Google Takeout ZIP file, subscriptions etc without needing a youtube account.
Also, remember the excellent TubeArchivist exists if you want even more control.
Well, my guess is as good as yours. :)
I was downloading some documentary series, probably the last batch with 50 videos did trigger this. Those videos were 360p though, not even high in MBs. But I couldn't download anthing after that.