I don’t know if this is helpful: I change settings in
Settings->Apps and notification->Default apps->Link open then set ON open link for instant apps.
From here, in Fennec 3-dots, and mayne others browser, you find “open in another app”
Unfortunately I can’t change this setting neither in fennec nor e’s system browser There is no popup menu showing up, in NewPipe’s settings I can though.
As said, it works for all links anywhere else than on the youtube website.
Sorry for being inaccurate, I meant “for” not “in”. I know, I changed the setting for NewPipe there, but i can’t tap or anything for the browsers in this system setting.
I even installed the youtube app for testing, if it is maybe youtube.com that won’t let me open in a different app for default, but it did not work either.