I have a NUC-like Win10 PCs running the few different TVs at home. One jellyfin server + NUC with a Firefox browser running a separate user for each room living \ bed \ work rooms lets each TV play the same content as I'm working around cleaning up and doing chores. The hardest choice was it to be an DS9 or Voyager marathon Easter.
Each client is able to play\ pause \ resume and it just works, they all respond.
Any different from the other SoC options fire stick/roku/etc - mostly only that I don’t have any of those to play around with, but through work I do have access to cheap NUC Like PCs.
I have a Bluetooth kb& mouse connected to each. Spacebar to play/pause works everywhere.
Audio is mostly in sync, but if you’re in a place where you can hear both TVs at once there’s a delay you can hear. I’m walking around with a Bluetooth headset connected to a TV that’s physically in the middle of my house to keep the reception mostly good enough.