Some password managers, like bitwarden, allow you to save Passkeys in them, and use them on multiple devices. That's the only practicable way I've found of using them. I need to use most services on multiple devices.

A) log in with passkey prior to device replacement, remove passkey temporarily, then re-add with new device

B) Set up multiple valid passkeys using separate devices, so that a single device failure does not prevent access

C) Use a portable passkey store like a Yubikey that is portable to any computing device

Personally I own two yubikeys; one stays on my person at all times, the other stays at my home at all times. I always add both when creating new passkeys for a service