Looks promising. Thank you!

Thank you very much! I will have a look at those.

well I would pretty much configure everything and my friends would simply „use“ the servers by connecting to it via the games (Minecraft, Arma etc)

Have you tried using ZeroTier? I don‘t have much experience using Tailscale but have been using ZeroTier for two years now without any problems. Runs great on Synology