There was a discussion here recently[0] where many people recommended Jellyfin in conjunction with its apps[1] for Android, Android TV, Roku, etc. I have never used Jellyfin before but their recommendations made me put it on my list of things to look into.
I’ll caveat by saying it’s been a while since I looked into it but last I checked the UIs weren’t super intuitive. This is a rare tech thing my entire family uses so that’s a much bigger factor than it usually is for me. I admit there’s also an extent to which Jellyfin can’t win here: my family always knows the Plex apps very well, switching would be a pain and (from their perspective at least) not have any notable advantages.