I am wondering what people’s solutions are for this conundrum. The simplest solution would be to just add this person as a user to my tailnet and have them access my sites that way, perhaps I could also limit access to certain cites by ACL e.g. the Cockpit web-management interface. I would, however, much prefer being able to just share-out my server node, and pick which services are served on their tailnet. Is this a plausible route to go?
Yes, you can create a second Tailnet in Tailscale and add your server without including your personal devices. You’ll have to create a separate account with a separate email address. Then you can join this second Tailnet with your server while leaving your other devices out. The separation allows you to manage connectivity and network policies independently.