By two factor you’re referring to the Signal PIN? If so, A) is there any real reason that you’d need to turn it off? b) where does it say you require a second Apple device?

Looking at the documentation though, I think I should retract my statement about Signal featuring iCloud backups... according to the docs 1) you can only transfer your data from one device to another and 2) the transferable data doesn’t include message history ️