The resources for this phone seemed to be scattered around the internet so I went ahead and wrote a simple on guide for it.
It covers: Rooting the phone, Installing Magisk (root), passing SafetyNet and debloating the phone. The phone is very barebones once you uninstall most of the apps! I like it a lot.
For the F21 Pro, there’s actually a surprising amount of resources that are up to date, much much more than for the F22 Pro.
https://github.com/AlikornSause/Notes-on-QIN-F21-PRO
And here’s a nice XDA thread too
https://xdaforums.com/t/guide-xiaomi-qin-f21-pro-custom-firmware-root-playstore-certified.4405615/
The F21 Pro is actually a really nice and capable phone, I like it. Even the 3/32 model is pretty useable. I mean really, no toll on performance.
Only thing with the 3/32 is that if you want to use ROMs, most likely you need to fully format the device EXCEPT THE BOOTLOADER, I mean other than that, wipe the whole thing down to nothing. It’s pretty scary, but then you can Format All + Download in SP Flasher for the ROMs.
Be really really sure you have backup of your factory ROM.