Using CTAP2, you can authenticate a passkey on any Windows laptop. macOS also has decent support (though not as seamless if you're not using an iPhone because of course it isn't). I personally do it when I need to boot Windows for something, using the Bitwarden app to expose passkey logins to my laptop.
Basically, when the system prompts to pick a key, click the "log in with phone" button, unlock your phone, and select the account/click "OK" to authenticate. The first time you do this, you need to scan a QR code to pair the phone to your computer, but after that you can use your phone whenever you need it.
Passkeys on Linux (and probably even more so on the more niche systems like the *BSDs) can use some love, especially when it comes to CTAP2. Chromebooks are probably the only Linux devices with native support for that.
If you want to safeguard against a fire, use a passkey provider that does exports (i.e. Bitwarden, KeepassXC) and then treat those exports the same as your password database file.
Basically, when the system prompts to pick a key, click the "log in with phone" button, unlock your phone, and select the account/click "OK" to authenticate. The first time you do this, you need to scan a QR code to pair the phone to your computer, but after that you can use your phone whenever you need it.
Passkeys on Linux (and probably even more so on the more niche systems like the *BSDs) can use some love, especially when it comes to CTAP2. Chromebooks are probably the only Linux devices with native support for that.
If you want to safeguard against a fire, use a passkey provider that does exports (i.e. Bitwarden, KeepassXC) and then treat those exports the same as your password database file.