I’d probably post quite a bit of content (music, etc) on a youtube alternative if I could expect it to not be copyright-striked.

VLC, for playing videos and other media.

I’m surprised nobody mentioned this, but I use mpv for the same. It barely has an interface, but it’s light and extremely configurable, and what I did was turn it into a picture-in-picture player (small, no border, etc, show subtitles if possible…). I use it to watch everything, including Youtube videos (it has builtin yt-dlp integration).

Or LibreTube, especially since Revanced needs Android 8+.

3rd-party Twitter clients are going to have quite a spike in popularity then, just need to implement clientside blocking. It won’t prevent the person blocked from seeing your posts, but that’s kind of impossible to enforce on a public platform, anyway.