Hello,
I'm in need of getting equipped with the right terms to look for and maybe some rough ideas. Networking isn't my forte, but I'm eager to learn.
What I'd like to put in place, would be some kind of wireguard nexus in a linux container on Alpine on a rental virtual server. (siteS)
I haven't yet setup an Alpine Linux server or anything in a linux container, but I'll get there. What to put in the container is something I could use some advice on, though.
Further, on several sites I'd have OpenWrt routers with public IPs, i.e. directly behind the sites' modems. Those I'd setup to on-demand (push-button or some local signalling) connect via wireguard to the nexus.
On the OpenWrt-sites I'd have different subnets/domains/zones (guests, private, management, wan).
Now, without any need to configure at any site knowledge about any of the others' networks, I'd like for say host "admin-pc.management.site-a.lan" to be able reach "switch-01.management.site-b.lan" by ip address but also by dns lookup. So, routing and dns-forwarding between same-category subnets should be automatically configured for all sites currently connected to siteS and different-category subnets should stay isolated from each other.
I realise, in the whole mix there shouldn't be two subnets (same category or not) with overlapping or identical ip ranges. And I guess, there's got to be some routing protocol for at least most of what I want. Say telling each other, who brings which ip range to the table. Probably also which domain it brings and the corresponding dns servers. ?
But also some zone category information/attributes/tags?
Or would I have to/should I for reasons setup one nexus per category and setup every OpenWrt router to make a tunnel from each of its zones accordingly?
I tried to get some overview of existing routing protocols, but those tend to be described by which problems they solve with which solutions and the names and abbreviations for those I'm often not familiar with.
So I could really use some pointers about what to look into. Which protocols/capabilities/config topics would be a good match to what I'm planning to do? Which software packages from the OpenWrt repos should I look into (like, what kind of sw is relevant and which alternatives each could be good picks)? Same for Alpine.
It should also support authentication methods for route advertisements, to be setup later.
It's not just about setting up something somewhat like it. I want to learn. So please hit me with the good stuff. 
Thanks for reading so far and regards,
Djoga'Ro