I haven't really looked into authenticator apps before, but with the increases in SIM-jacking I think it's time. I don't use Google, so Google Authenticator is out. I use Duo at work; can you use that for arbitrary personal services? Are there others apps that come recommended?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 appreciatedEdit: 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:  Based on this I'll probably go with Authy