This task seems to be missing an understanding of how exactly TOTP works. In particular, the linked "authy" thing appears to be a much more complex version of 2FA that requires using their third-party service and incorporates TOTP as one of its several options. The TOTP option in their app could be used with the OATHAuth extension, but there would be nothing for WMF to "host" for that to happen.

I see little point for WMF to spend resources in creating a TOTP app when open-source apps like FreeOTP and totp-me already exist.

Agreed this would not be a good use of time. We don't host any browser either and people have no trouble finding one that suits them.

Leveraging our existing mobile apps is an interesting possibility (e.g. if you have Google Apps on your phone and do something 2FA-worthy in a browser, it just shows a notification on the phone and asks you to press OK if it was really you) as it offers a more streamlined UX that would not be possible with a third-party app. Still, it does not offer enough benefit over a random 2FA app to justify the effort IMO.