No wonder, I recently installed the latest sonoma beta and couldn't for the life of me get Mullvad to work. Glad to hear Mullvad is working on a workaround. I even considered downgrading back to Ventura this morning. I feel validated!
Went to look at tailscale vpn and didn't realize it was a service entirely contained within tailscale, so I can't use my existing Mullvad account or credit tailscale with my already-purchased Mullvad credits :(
I don't think the service is so much "tailscale for mullvad users" but the other way around, it's intended for existing tailscale users to get an "exit node" of sorts in their tailscale network without having to set it up themselves.
Tailscale's business model has never been anonymity, last I used them they even required either a Google or O365 account to even use the service.
You might want to look into Headscale[1] instead, it's a server-side implementation of Tailscale that you can self-host. It comes with its own drawbacks but from what I've seen it's worth it if you want more control over the network.
I have seen a case where they substituted the credits on Mullvad to the add-on for Tailscale, but this might not be a regular thing.
Although, it is also still in Beta and issues have been reported/known, so similarly if you look for a stable solution it might be best to hold out for now.
