I am beginning to suspect half the issues with 3rd party password managers not being able to detect and/or autofill login or registration fields is due to the erroneous Orion keychain button.
Regardless if you've disabled the Orion keychain option, the overlayed button for it remains, but does nothing and disappears when clicked.

When Orion keychain is disabled, the keychain button should be completely removed.
0.99.126.3-beta (WebKit 618.1.2)
Sonoma (14)