NMap through a terminal emulator like Termux?
It was indeed carrier locked, which was why I used it as trade-in value for a phone rather just selling it and later buying a newer phone.
In my case, AT&T sent me a Galaxy Note 9 to replace my Google Pixel XL, which I ended up never using and just used a trade-in value to get a Pixel 5a.
NMap through a terminal emulator like Termux?