It's the only reason I want to replace Tailscale with something else or look into self-host when have a bit of time during my vacation. They only allow login through a third party, which is a big no for me.
Tbf to Tailscale they allow any OIDC provider[1]. I wish this was more normalised, then we could have one login everywhere regardless of who hosts it (even if it's yourself).
While that isn't convenient is you don't want to use the public identity providers, it should make you think about what makes your identity on the Internet, and consider to have your own identity provider on a DNS domain you control.
I created my own AWS Cognito userpool just for tailscale. I recall the webfinger redirect was frustrating to get right but I refused to use Google/Apple as a gatekeeper to my own network so I had all the motivation to get it working.
You can host your own identity provider. Authentik, Keycloak, authelia or Zitadel work.
I don’t fully agree with tailscale’s decision to not want to be an identity provider but I understand it on some level. It simplifies their service greatly and the amount of asks for that will essentially have them build a full enterprise Entra-like solution that would be a constant maintain headache and they are not interested in that.
Beyond simplifying their service, it allows Tailscale to have reduced responsibilities (because of reduced collection of sensible data), and makes them a less interesting target for people wanting access to the data (wether illagally by hacking, or legally from government agencies). This probably makes them less attractive as targets for censorship.
[1] https://tailscale.com/docs/integrations/identity/custom-oidc