Lets drop a flag for @brian to comment. I fear, however, that there may not be much to be done. VPN is not officially supported and, as I understand it, is unlikely to be the preferred method for a long distance solution. It may be that other users who have used a VPN can assist.
I know that some people use VPNs successfully–TCP and UDP traffic must pass between the two machines freely, as if they were on the same LAN. Anything that might impede this (bad VPN, misconfigured VPN, or firewalls) is likely to break private zone streaming.
This piece of the system just wasn’t architected for remote access, but if you can get it working, it’s fine to use it.
We’ve discussed some neat ideas/architectures to solve the problem well. A remote access solution (that will not require a VPN) is on the roadmap, but we haven’t put a date on it yet.
I still use LMS for remote access - haven’t been able to get VPN to work with Roon. Looking forward to seeing Roon’s solution to this. It’s not critical to my use but Roon has spoiled me and it’ll be great to be able to use it remotely.