I doubt this is a thing, but is there a VPN tunnel like headscale//tailscale that allows a person to approve a client connection from the app or elsewhere for another device without it? I’m asking because I want to use devices like tvs with jellyfin but behind tailscale as well. Is this a thing? I don’t know exactly how the app works, so don’t crucify me lol.
I’m a smidge confused on what you are trying to achieve and how you think it will work.
As I understand you, you want to connect “embedded” devices where you do not control the software to a VPN network?
VPNs do need some kind of client (otherwise how does the network stack know to use the VPN protocol?) so how do you envisage this working without an app?
What is your desired topology like? Do you just want your smart TV/etc to connect to a remote media library over a VPN? If that’s the case, then you are overthinking it with approvals etc.
You can achieve most of what you want with router configuration. Just define routes saying “Traffic from IP address 10.20.30.40 (TV) should go to 10.20.30.30 (gateway)” and then have the “gateway” handle the tunnel.
You can also look at tailscale’s subnet routing (should work with headscale backend too).
Good luck.