Making home asssitant accessible online (ideally via an OpenVPN client)

What caveat? ZT works perfectly in exactly this scenario.

I believe ZT doesn’t quite like Double NATs.
https://zerotier.atlassian.net/wiki/spaces/SD/pages/6815768/Router+Configuration+Tips

My WWAN router performs the 1st NAT and the ISP does the 2nd NAT for them to conserve addresses.

Have you even tried it?

Yes I have.

All my other sites on FTTH have no issue.

Which ISP do you use for the mobile link? If it’s Telstra maybe you could use IPv6 and avoid NAT…

Unfortunately I’m not in AU and the ISP I’m on restricts consumer grade LTE.
For them to allow access to a public IP from their pool or have IPv6 functionality needs an upgrade to their LTE for business offering which is pricey.

Well that sucks. When you said FTTH I thought you were in Aus.

Yeap it does suck. FFTH is pretty common in other parts of the world as well
Anyway, hence the need for VPN Client functionality on this particular instance of HA.

Thanks for the sanity checks though. Trying to sort through my options, and NC being the last option. Although not keen to be managing multiple logins for multiple instances

It’s odd NC works if ZT doesn’t…

Planning to test this soon as well. But i believe the traffic initiator is the HA rather than NC. Will update once I fire up NC free trial for this site.

Well same with ZT… all devices are clients that log into ZT server which establishes P2P between them all… Maybe NC does it differently…

I mean having a VPN server outside of your network and all clients connecting to it from inside of your home network - I’m on 4G myself, so no inbound connections available either.

I’ve got a seedbox with OpenVPN on it in Europe, but as I said the Android client or the seedbox itself seems unreliable.