@KJU said: About adb&fastboot from the UT terminal, though, any such barrier there? There shouldn't be, no. I happened to pull a file from one UT device to another via ADB. So I know that works. In haven't tested fastboot myself, but I see no reason it wouldn't work.

Kubuntu 20.04 LTS running on my laptop does a very good job at recognizing many phones via ADB without any issue! However when I need some Windows tool(s) for specific phones or issues I use a older laptop that is running Windows 7 Home 64-bit as my "Dedicated Phone Flashing Machine" Also : After flashing a Custom Recovery you should simply tell the phone to reboot into the OEM Recovery and not from the Image File on your PC So try this : fastboot oem reboot-recovery For more info see here for example : https://forum.xda-developers.com/t/recovery-3-4-0-10-davinci-official-unofficial-twrp-for-xiaomi-redmi-k20-stable.3960726/