I haven't had any problems with syncing and using passkeys with 1Password and Firefox on MacOS, iOS, or Windows. When the site wants to create or use a passkey I get a prompt from 1Password on the device that I'm using. No need to involve a second device (which for me I'm fine with security-wise. If I really wanted to be sure there was no way of malware extracting the keys I would be using my Yubikeys)