When enabled, a failed or cancelled request to KeePassXC will trigger the browser's own internal passkeys request.

This is a little convoluted. Please bear with me:

Using a YubiKey for MFA with CloudFlare with "Enable passkeys fallback" enabled in the extension:

• If no passkey exists in the keepassxc database fallback seems OK; the browser takes over and lets me use the YubiKey.
• But with a passkey present in the database, dismissing the passkey credentials dialog generates an error in the extension, but doesn't fallback to the browser:

KeePassXC - 2.7.10
KeePassXC-Browser - 1.9.7
Operating system: Linux x86_64
Browser: Mozilla Firefox 137.0