Passkeys are built on the FIDO2 standard (CTAP2 + WebAuthn standards). They remove the shared secret, stop phishing at the source, and make credential-stuffing useless.
But adoption is still low, and interoperability between Apple, Google, and Microsoft isn’t seamless.
I broke down how passkeys work, their strengths, and what’s still missing


Tried Passkey in the past. I had many problems, especially could not understand why they must use my google account. Now my google account is gone, don’t gonna go that rabbit hole again, i am happy with my Bitwarden and Aegis.
Bitwarden does support access to access keys in (for example) firefox.
I have not tested outside of browser (firefox). So it may depend on if you use chrome or some other app.
Edit: Just got a suggestion inside the Amazon app (Android. Yes, I hate Amazon as well but I got a gift card and I hate it even more to give them a free of charge credit) to add a passkey. So it seems to work (semi-)reliable outside of a browser.
You can now use thirds parties APIs for Passkey. I use ProtonPass on my part, it works great most of the time, but there are still some apps that have Google provider hard-coded.