> One slightly more concerning issue today is that there is effectively no way to export private keys between authentication password managers
Not being able to use the passkey manager at all is a bigger concern. For example Keepassxc works with some sites but not with others. It's super annoying and way worse than situation with passwords.
I use Bitwarden and have never had issues saving or using passkeys with any site I can recall via the Chrome extension.
Well, see here: https://github.com/keepassxreboot/keepassxc/issues/10374
I'm pretty sure a lot of this stuff are arbitrary decisions that sites make when they implement passkey support and you never know where it will work. Also some sites likely don't care about fixing it since they think they deliberately are "improving security" or they just don't care. So I'd say it's an ugly mess. I wish it would work though.