You have described it so often in a really helpful way, why not put it together for a tutorial in the Question & Answer forum section? Then it doesn't always have to be repeated so often
ADB commands worked; only fastboot didn't.
Command fastboot devices get empty.Only when I command fastboot via the Mi Flash Tool driver installer does it respond. When i disconnect the phone and reconnect in any USB port, fastboot no longer reacts in cmd
The same with me. Under win10 the Mi 10 is not recognized in the device manager with Fastboot and consequently does not accept commands. The win10 android bootloader interface driver does not start.