Conclusion: youtube links to channel sub-links with more than 5 characters are invalid.
https://www.youtube.com/@domegaia/about
https://www.youtube.com/@domegaia
https://www.youtube.com/@domegaia/chann
https://www.youtube.com/@domegaia/12345
https://www.youtube.com/@domegaia/123456
https://www.youtube.com/@domegaia/abouts
https://www.youtube.com/@domegaia/channels
https://www.youtube.com/@domegaia/community
https://www.youtube.com/@domegaia/abc123
https://www.youtube.com/@domegaia/shorts
https://www.youtube.com/@domegaia/featured
https://www.youtube.com/@domegaia/videos
The youtube regex matches the links that have more than 5 characters at the end.
Not sure if it's the best way or if you want to handle it differently. As far as I can see these are not links to videos so they shouldn't turn into embeds.