You can also use Microsoft now (both "personal" accounts like used for Xbox/Outlook and "Enterprise" accounts like Microsoft365 and other AAD based accounts)
I'm sure if you asked them about switching auth methods they would help with that.
That’s a good point. I’ve sent them an email and I’ll see what they say.
EDIT: since I’m still in the edit window, here’s what Tailscale came back with (great response time!).
>We can fairly easily switch between auth providers where the usernames are an email address, like Microsoft or Google or Okta.
>For GitHub the username is different, GitHub uses your Profile name. Any email addresses associated with your GitHub profile are not available.
>Unfortunately there isn't a straightforward way to migrate an existing Tailnet with its devices from Google to GitHub. We generally recommend making a new Tailnet with GitHub and re-authenticate devices using GitHub one at a time. For remote devices, this is more challenging.
>If you want to try it, a suggestion:
1. you can create a Reusable authkey at https://login.tailscale.com/admin/settings/authkeys for the new GitHub Tailnet
2. Over ssh to a node currently on the Google Tailnet, you can:
`tailscale up --force-reauth --authkey=tskey-0123456789abcdef`
3. You'll lose the SSH session. The device will make a new Node key and be issued a new IP address on the new GitHub Tailnet.
4. You can look up its new IP address on https://login.tailscale.com/admin/machines of the GitHub Tailnet, and should be able to ssh to the new address.
I'm sure if you asked them about switching auth methods they would help with that.