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
there's still vaultwarden. i just self-host that and use the official bitwarden clients (android app + firefox extension). even if bitwarden itself shits the bed and takes their clients down with it, i don't doubt there will be alternatives up and running relatively quick.