Finally got around to actually trying out ZeroTier. It's pretty awesome!
Okay, it has a couple downsides:
- it's not automatically a mesh network, you have to designate a node as a "moon" to make it pass traffic between other nodes (that couldn't punch holes through NAT)
- the Android client is not open source and doesn't have UI to tell it to orbit a moon
But other than that… the simplicity is lovely. No screwing around with config files, restarts and whatnot. Just a very small & easy set of admin commands. And automatic IP address assignment (especially 6PLANE) is amazing.