Are ATT iPhone 13's universal devices and could work with any carrier?

Hello ATT Community,

I bought an iPhone 13 Pro Max through ATT that was also the "ATT" version but after paying it off, unlocked it through ATT.

My question is - now that it's unlocked through ATT, is it's compatibility the same as a factory unlocked iPhone 13 that was purchased through Apple? I.E. Is the phone now fully usable on either Verizon or ATT for example.

Any help in clarifying is appreciated. Thank you!