on iOS, at least, the Tailscale app will pop up a push notification for you to authenticate in that case; I'm not sure if the same is true on Android but could be worth checking your notification settings.
Notifications are enabled for Tailscale but I don't get one to authenticate.
I was just able to work around the issue by installing Termux which provides a small Linux environment on your phone. I was able to use openssh in the Termux environment to connect and get the authentication URL. After that my preferred ssh app can connect without issue.
I was just able to work around the issue by installing Termux which provides a small Linux environment on your phone. I was able to use openssh in the Termux environment to connect and get the authentication URL. After that my preferred ssh app can connect without issue.