I’m surprised you haven’t checked out ZeroTier (.com)
Very easy to setup and has clients for just about everything even including my Asus router via Asus Merlin.
Basically i have an always on private network which if i had access to the router where i currently live, i could route it directly (peer to peer) instead of using ZeroTiers cloud as i am at the moment.
It’s also very handy when i’m out and about as i can SSH in, RDP in etc etc.
100 clients on the free tier - i have 7:
2 Linux Mint PCs
2 Macs
2 iPhones
1 Asus Router (edit: in repeater mode)
And you can also configure up more than one network, invite people to join, and also configure public networks too.