[keverets]

For the US and Canada, there is JMP.chat which can be used to 2FA over SMS without a SIM. Uses standard XMPP so can be used from a computer or phone while on WiFi.

There are other proprietary services which can do the same for no monetary cost (usually lots of advertising and tracking, though).

[icebraining]

Of course, that means you're giving "Denver Gingerich and others" full access and control over the number and channel used to receive unencrypted authentication tokens.