GitHub Becoming 2FA
GitHub is switching most of the sites now to 2FA. The warning has been out there since at least 2023. Just now, on my current team’s site, have I gotten the message. Our organization is now doing this.

Check it out here on GitHub.
As of March 2023, GitHub required all users who contribute code on GitHub.com to enable one or more forms of two-factor authentication (2FA). If you were in an eligible group, you would have received a notification email when that group was selected for enrollment, marking the beginning of a 45-day 2FA enrollment period, and you would have seen banners asking you to enroll in 2FA on GitHub.com. If you didn’t receive a notification, then you were not part of a group required to enable 2FA, though we strongly recommend it.
You get a few choices in GitHub:

I decided to use a software authentication app on my phone, here are a few you can choose from:

And away you go.