Started to move off Google’s services to proton:
They’ve announced they’re trialing the custom app currently, after which they’ll discontinue the IMAP/SMTP bridge.
I’ve just skimmed through the proton blog briefly and I couldn’t see anything referencing this. Do you have a link by chance?
It’s in restricted beta currently, only available to a small category of users, and still lacking features. They say it will launch early 2024 but it looks more like mid-year to me (at best).
Point is, it won’t happen very soon, but it will happen