Can not log in Xiaomi / Google accounts


Jan 1, 2023
I have started to struggle with my Redmi Note 8T yesterday because fully functional phone (all the hardware -wifi, bt etc. - work) is not able to sign into existing accounts.
I know all my passwords, I can log in these accounts in browser (both at PC and this device).
Simply, phone is not able to connect:
- to existing Xiaomi account (both original one, and a newly created)
- to Google accounts (nor simple password, either 2 phase verification)
I have cleared data for Xiaomi account app, rebooted devices several times...

Any help/hint/idea greatly appreciated!

Redmi Note 8T, Android 10QkQ1.200114.002, MUIU Global 12.0