that exit node will essentially need to work as a router, connected to both the tailnet and whatever other VPN peer you are working with. you could also use something like a gluetun container as I think it works with a wide variety of popular VPN providers.

Yep. I had it set up in a docker compose setup with tailscale and gluetun. There is actually decent documentation for this on gluetun docs i think.

Then your tailscale container exists via gluetun which connects to your VPN.

Edit: Found these

https://unix.stackexchange.com/questions/786512/how-to-enable-direct-connection-to-tailscales-exit-node-with-gluetun

https://lemmy.world/post/7281194

I'd say you install the VPN on the home machine, then when you turn on tailscale on your phone, the traffic should be Phone->home machine (exit node)->VPN