if you're using Burp, here is a tiny bug, the patch should be in the next release: In the Login Recorder web extension, the algo of Public keys is not casted as an int. Thus, a buggy website sending the only supported value as a string will get an error.
Here is the small patch:
In the ${Burp_Install_Directory}/navigation-recorder/background/recorder-service-worker.js, replace:
if(!t.pubKeyCredParams.some(e=>-7===e.alg))
with
if(!t.pubKeyCredParams.some(e=>-7===parseInt(e.alg)))