Xiaomi has fake unlock. It has an unlock button that never works and never has worked. Instead you have to write a letter to get their approval code or some complete bullshit like that. Of course this is because unlocking is illegal in China and they sell a lot of phones in China.
- non-US Samsung phones
- Most Sony, HTC, Motorola are unlocked
- Chinese brands like Xiaomi
Not all Pixels are unlocked; carrier-bought US phones are usually OEM locked.