That’s pretty much how SMB in general works, but (assuming synology supports it, I’m not sure) you can force privileges for the files at the server end. In your case that would pretty much mean rw privileges for everyone, so it’s not ideal (security wise), but if your environment is suitable and that’s a compromise you’re willing to make it is possible. Also you could check if setfacl suits your needs.
And then of course NFS, but that has a tradeoff that if you need to access files with anything else than linux-box it’s not ideal either, specially if you’re after fine grained privileges over multiple systems.