Back when I last looked you had to register an account, use a Windows application and wait a few weeks before being allowed to unlock the phone. Has that been changed then?
Though most of the brands (except Nokia and Samsung) seem to have pretty reasonable terms for unlocking the bootloader and aren't as ass-backwards as Xiaomi's.
[1] https://xiaomitool.com/MiUnlockTool
[2] https://forum.xda-developers.com/t/tool-win-lin-mac-miunlock...
Xiaomi once conducted a poll on Twitter which OS users prefer - MIUI or Stock. 80 % or so voted for Stock Android hence Xiaomi deleted the poll.