Really interesting read about the history of YouTube adblocking, how the new detection works, how uBO is responding, and how not to block the new popups.
Libretube is usually broken in some fashion (often a fatal one, like failing to load video).
LibreTube isn’t broken, it’s the Piped instances that have issues. You just need to switch to another Piped instance in the settings. Click on the three dots, then select settings, go to ‘Instance’ and at the top you can hit ‘Choose…’ to change the Piped instance. I haven’t experienced any issues with adminforge.de. kavin.rocks also seems to work well.