Infuse is what I recommend. It won’t play music but It’ll connect to plex, jellyfin, or emby. Has a good UI and can direct play anything you throw at it. The only issue you will have is transcoding. It will NOT request your server to transcode so if you are outside your house and have a bandwidth limit on your remote streams it’ll fail to play.
My assumption is, plex amp will expand to the appleTV since they are taking it away from the main app. I could be wrong though… plex team hasn’t really been listening to its users as of late.
They have apps for AppleTV, iOS, iPadOS, macOS, and even appleVison.