to use as a media centre and multiplayer gaming system in my living room
Based on this, you’re basically looking for the ‘game console experience on your couch’. If that’s the case, honestly you shouldn’t look beyond^[1]^ Bazzite.
If, instead, you actually wanted to play retro games primarily, then please let us know.
While ChimeraOS and HoloISO also offer the ‘game console experience’, they don’t support Nvidia GPUs. So you would be on your own at best; which would be a horrible experience for a new user. If you feel particularly adventurous, then Jovian-NixOS is actually another option. But arguably less newbie-friendly compared to Bazzite.