Seconding the suggestion to use an accessibility service to detect fields to autofill. Microsoft Authenticator used to do that really well, before they killed the password manager aspect of it.

Sucks that android os and android app developers make it so difficult.

A gazillion times this!! Bitwarden handles this very well, if there's an email field without a password field, still offer to fill it.

Yes, some apps seem to have spotty support for the built-in Autofill service.

I think too that this can happen in various "flavors" where either:

1) Neither field is recognized, so one must launch Proton Pass manually to copy/paste from
2) The username/email field does not prompt autofill, but using autofill from the password field will fill in both spaces
3) The username/email field is not recognized at all (for filling or launching autofill)
- one must fill in the username/email via copy/paste, but need an open instance of Proton Pass to switch to/from, or must fill in by hand.
4) Some applications will simply fail to autofill from the autofill service after selecting login, but the autofill service dismisses because the field is supposedly "filled" (seems more android dependent, as this is more prevalent in recent versions, e.g. 13+, and not just for Proton Pass).

For the last two cases, I think that keeping Proton Pass in memory/"recent apps" would allow the user to work around this by switching back to the instance to fall back to copy/paste.

For the 2nd/3rd cases (and somewhat the first), other password managers make use of Accessibility services to create additional prompts if a built-in screen reader sees username/email/password fields. This can make up for poor implementations of the autofill service in applications.