alt Hacker NewsCopying / syncing passkeys between password managers is still work in progress, but you can usually work around it by making multiple keys. For important websites, I recommend saving additional passkeys to Keychain, etc, as backup, assuming the website allows that. (It should, but some websites might not have a good implementation.)
Also, nothing says you have to delete passwords (or alternate means of logging in) if you already have them set up. Having multiple ways in will help prevent lockout.
Unfortunately probably implementation specific, but you don't always need to have multiple passkeys. There is cross device passkey login. I had this occur in the last couple weeks. Evidently I had created a passkey on my phone. Logging into that site on my PC, it identified that I had a passkey and allowed me to authenticate using my phone.