@CzZ Make sure that you have Android 10 installed on your Phone before using UBPort installer. I have been through the same and tested with several andorid version (14,13,12,11,10) on Redmi Note 9 Pro. Finally it worked flawlessly on Andorid 10. I was running UBPorts installer on Ubunut Mate.

@MrT10001 After Rebort System, the phone will restart and then enter the fastboot interface. adb is Scanning for devices will appear in the downloader. If the phone is restarted, it will remain stuck in the fastboot interface until the system is reloaded