I've cancelled my subscription yesterday, conveniently it was about to renew at the end of the week, so I have a few days to migrate from Proton, here's what I'm thinking of, but I'd love to hear what other people are switching to
Solokey and Nitrokey are strong alternatives, and the two I’ve been recommended by people who would know.
Solokey is good if Fido is the only thing needed.
Nitrokey has Fido and more. I keep meaning to try the other features, but haven’t gotten around to it.