After many hours of frustration and bootloops I found the solution for installing custom ROMs for the first time on my Mi 10 T Pro. It always involves losing your data. I am in doubt that there's a good process at the moment that'll allow you to keep your data when moving away from the stock ROM. The process goes like this:
1. Put the phone into fastboot mode. Do not install any TWRP but simply boot into it with i.e.
Following a different guide, I installed TWRP and now my phone is bootlooping. How did you get out of that? Did you flash a stock recovery? If yes, which one? Thank you!