I dont agree with many things apple does at all, and I also think their password manager has flaws like revealing usernames without authentification.
It is pretty handy though, to have a file where the entries are stored unencrypted, and if the password manager detects an entry it prompts to decrypt exactly that field, maybe with a fingerprint.
KeepassDX needs to run in the background and be completely unlocked to even detect apps or password fields.
Do you know any existing app that can do this?
Yes I already use these. On Linux I use Kwallet, store my huge random Keepass password in there and unlock the Keepass database by fetching that password using a shortcut.
But still, then the password storage is open. Not as elegant as an on-demand password requester, especially on Android