@Edent I've considered it for an APRS to Fediverse service.

In the world of amateur radio we're not allowed to "obscure the meaning" of a message which rules out encryption, but we'd also want to assure a message was coming from the real user, but we don't want to send a password.
TOTP is also easy to generate and enter into any handheld radio up a hill, unlike a PGP signature etc.

Given the restrictions of a short message, no encryption, minimal hardware requirements, TOTP could work well.