Also, just general questions: are these apps usually free (if not, free isn't a hard requirement)? Is there some standard, or does each service only support a subset of apps? What happens if you lose your phone?
Any info is appreciated
Edit: One more question: I see rumblings from some people about using password managers as an alternative to 2FA apps. Is that a valid strategy? Does one make the other redundant?
Edit 2: I found this excellent deep-dive on the overall mechanism and the major players: https://arstechnica.com/information-technology/2020/05/choosing-2fa-authenticator-apps-can-be-hard-ars-did-it-so-you-dont-have-to/ Based on this I'll probably go with Authy