FIDO2 key

I would guess it would depend on how you set it up and what you use it for.

As a way to log into windows - it could be one of a number of permitted login mechanisms. If you set it up for 2FA on a web site etc, then it would then come down to how the web site configures its security and what mechanisms there are for recovery from loss of 2FA. It might not be a process that is easy enough to routinely want to do without access to the 2FA token source.

Some websites use 'security codes', which are means to bypass the 2FA if missing.

Another approach is to set up a password manager and then use the reader as a way to unlock the password manager, rather than registering it with each specific website. The manager might offer alternative ways to unlock that don't involve the reader.

(password managers can also hold TOTP secrets, which websites use for 2FA, not just passwords)

Theo