The login/password is almost never auto-filled by this extension in websites login/password fields. It works only on a very few sites (like Paypal for example).
I tried with the snap version, and the ppa version of KeepassXC, I got the latest version of it, ran the script when needed, nothing worked.

Keepass2 with Kee extension works perfectly on every webpage, so I went back to it. Shame because the installation of keepass2 with mono on linux is a pain, compared to the simple snap install of KeepassXC.