Yeah, YouTube is once again doing some shenanigans. My home IP address is not blocked from the YouTube site, and certain invidious instances are working. yt-dlp has the same issue as NewPipe (asks for captcha, sends back 405 by default). Using a VPN seems to solve the issue.
I was a bit afraid that YouTube just outright blocked my IP, as others in my household use YouTube. Luckily it's just NewPipe and yt-dlp, and a VPN solves it.
Nevertheless, it doesn't bode well that YouTube is going to such extreme measures to prevent NewPipe/yt-dlp access.