I had to go to an AT&T store, port my phone number to a different iPhone, restore from an iCloud backup using the SMS 2FA, and then I could finally log into 1Password for my passwords and MFA.
If I didn't have a memorable iCloud password this would have been impossible without the 1Password recovery paper.
Devices are often lost/stolen on vacation where the myriad layers of protection are extremely hard — if not impossible — to penetrate.