I agree there should be more explicit support here, but can this not be "solved" with backup codes? One or more could be given to a trusted person – a family member, a friend, or even a trusted librarian – or a backup code could be remembered.

The tough issue here is that these access edge cases look a lot like malicious use. The aren't but authenticating someone who has no device or ID or really much else to authenticate themselves is a Hard Problem. Passwords also aren't the solution here, the industry is moving away from them precisely because they provide poor authentication, particularly for vulnerable people.