This is an add-on I tried to add some time ago but didn't work at the time. It now is working and I've been able to use it without issue.
It's worth noting the options are fairly limited, and doesn't support YubiKeys / similar, just TOTP generation, so fine for google authenticator and similar, but not going to play nice with hardware / other types of MFA.
I'd strongly recommend everyone enable this from a security perspective, and staff should expect in the near future that this will be mandated for staff in policy.
To activate, login to the forums, click your profile at the top right and click "Settings", click "Two Factor" and scan the QR Code (Or click Manual if you use apps that don't have scanning functionality) and it'll prompt you for your password and the TOTP Token at that time.
Any issues with it let the forum team know, but it should work for everyone at the moment.