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
I assume the point of the extension is to have support for autofill, if that is the case, you should be aware that it is generally a bad idea to give your browser access to that info directly since they are the definition of internet connected apps. What I do instead of autofill with keepassxc is open the vault and press the copy to clipboard buttons which works essentially the same way as autofill just with a couple more clicks.