Jellyfin is fine if you direct stream only, but any form of transcoding will kill your server. It is a bit hard to get other people to download the desktop Jellyfin Media Player or Infuse on iOS, and I don't think Android has a version of the app with massive codec support.
Jellyfin does fine transcoding 4k on my decade old i7. And it'd probably be a hassle to install it on other people's phones, but the Android app can use MPV as it's media player
