1password works just fine with OTP across all my devices.

Using an authentication method tied directly to and dependent on my phone seems extremely risky and short sighted. A phone can be lost, fall out your pocket into a toilet, etc and those are just accidents. They also basically have a max life time of five years. What happens when you buy a new phone?

Well yea, but many big players do that: Google Authenticator, Microsoft Authenticator, Duo, Okta, etc.

You use 1Password as your authenticator as well? Doesn't that make it not multi-factor if it contains both your password and authentication?

The 1Password database is something you have. You unlock 1Password with something you know or something you are.

Does that answer the question? If you have a password and key for 1Password, and keep both your passwords and authentications for accounts behind that password and key, doesn't that defeat multi-factor authentication? Because if the person has access to your account password within 1Password, then they also have access to your account authentication within 1Password.

Factor means something you have, something you know, or something you are. 2 are needed to access 1Password.

Storing everything in 1 app makes the app a single point of failure. Storing everything on 1 device makes the device a single point of failure. Single point of failure and single factor authentication are different.

KeePassXC is a TOTP authenticator and it saves to a file. You can put the file anywhere you like. You can, given the correct master password, open the file again on any device and generate TOTP codes.

Not OP, but I use Aegis [1] for 2FA which can create encrypted backups. They're synced automatically to my NextCloud instance with the NextCloud app.

[1] https://github.com/beemdevelopment/Aegis

2fas backup to iCloud

https://2fas.com/