Search for sendspin, ist an opensource protocoll for spreaker sync. I have a setup together with Musik Assistant and i can perfectly sync musik on my laptop, phone , yamaha stereo and selfbuild speaker. You can have then in the same room and enjoy the musik.

As a novice DON’T put your devices on the open Internet. Use something like tailscale or Splittunnel. You can give your friends access through that.