I needed to create a backdoor network-level KVM contraption to help my dad relocate some servers. tl;dr an office was closing down, he pulled the rack and stood it up in his basement. I mailed him a unifi edgerouter 4 that was reflashed to run openbsd. On boot it would create a vpn tunnel to a vps and basically expose a public WAN port to the rack. So it was in my dads garage on his Fios internet, but from a networking perspective it thought that it was in a Linode datacenter.

The ER4 has 3 ports: 1 was for the uplink, one exposed the WAN connection to the rack, and then the 3rd port became a client inside of the network. I could shell into it from home (he's on the other side of the country) and operate from the residential network and also the server network simultaneously. Worked well enough for a few weeks to keep access around until we could engineer a better solution.

Configuring OpenBSD was really quite simple and rewarding. No insane linux network stack / netplan / cloud-init / bs ... just a few conf files.

obligatory pic: https://i.imgur.com/Mkf9ckc.jpeg