Selfhosted

That is what it seems like based on what I have read :/

I guess the best option in my case then is likely to add them as a non-admin user to my tailnet. The only concern I have is with the potential of one user deactivating the VPN connection unkowingly, which is probably where Funnel comes in as a better option, but I would prefer to avoid serving stuff on the web when possible. (It is specifically a FreshRSS instance for now)

It's problematic, but possible: https://jamesguthrie.ch/blog/multi-tailnet-unlocking-access-to-multiple-tailscale-networks/

Yes, there is two ways you can go about this. The way that you are thinking of (and the way that I would ideally like to go about this) is as listed on this help article. This is perfect for sharing a home server to some friends, and letting them access a given service without seeing any of your personal devices.

The other option is to have just one tailnet, but having multiple users as detailed here. Notably this can be a security regression (if you don't limit access on a per-user basis with ACLs), but is ideal for sharing access to your entire network with your spouse / older children within the context of self-hosting.

For example, I have a friend who has shared a minecraft server with me and that is an ideal example of sharing one node to a seperate tailnet. I am an admin of the server, and can manage the docker container for it + the backup sidecar and the SMB share, but that is where my access to his network structure ends.

This contrasts the situation with my partner for example, where we share a tailnet (with seperate user logins) to make things like gamestreaming just that much easier to setup. Hypothetically I can use ACLs to limit access to stuff like the Cockpit web-management portal, or block the SSH port, but I don't feel like I need to in my specific case.

Addendum: I also think sharing the device out strips it of its subnet routes + services, which is part of the problem I am running into where I do want it to strip subnet routing (my elderly parents DO NOT need access to my printer), but I ideally want to be able to still use tailscale serve + services + https certificates to be able to share my self-hosted RSS feed reader for them (ad-free, no AI slop, much better for my one parental figure with early-onset dementia).

Addendum 2: I highly recommend exploring tagging + ACLs if you are looking into personal usage / seperation of networks. It is just a much easier approach of seperating devices that are owned and operated by the same person. I would only explore multi-tailnet option when it is different users and you want to share a very limited scope of your network.

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.