> Aren't they effectively locked in the database of whatever password manager is used?

Not in the case of Keepass, since you can export them.

> I know you can export them, sort of, but that feature may blacklist your password manager and make it useless.

Yes, and this is why passkeys are flawed.

> Are they portable? I thought passkeys are locked to the device.

There's nothing preventing you from syncing your passkeys and using them on different devices. This even seems to be the happy path in the locked down eco systems (You can create a passkey on an iPhone, which is then synced to iCloud, and now you can use that same passkey on a Mac).