Just found netmaker, it seems like it's pretty much exactly what I'm looking for in order to handle communication between our edge nodes. I just have one question, which is am I able to join the network without announcing any ranges? Seems like something we'd just deploy on the same machine as the edge nodes, so there's no reason to assign a whole range to the node, just the single IP

yes, when you deploy a node, it gets 1 private ip by default, not a range.

Ahh, I think I must have been confusing the standard config with an egress gateway then

yup, you can add an egress gateway after the node has been deployed

Does there happen to be any integration with routers or FRR?

not yet no

Fair