(last commit from Dec 11, 2022)
The PR isn't dead though. There's some additional discussion[2] on its current state in the issue I linked above. Basically, it needs more people to test the implementation against different sites in the wild.
Hopefully the increasing popularity of passkeys will provide the necessary level of motivation and support to get this over the finish line.
[1]: https://github.com/keepassxreboot/keepassxc/issues/1870
[2]: https://github.com/keepassxreboot/keepassxc/issues/1870#issu...
Of course the pull request is pending review but that's not too exceptional.