Associate
Is it necessary to unlock the bootloader to use ADB? I keep getting error messages including 'The device is temporarily restricted'.
Xiaomi Redmi Note 4 - Just in case this helps someone else I finally figured it out, I must be extremely stupid as I eventually realised that it was a permissions problem.
To enable 'Install via USB' and 'USB debugging' from Developer Options you need to connect to the mobile network rather than Wi-Fi and also be signed into your Mi Account to allow the necessary permissions to be granted. Additionally 'Turn on MIUI optimization' needs to be disabled and the phone rebooted and not forgetting to change the default battery charge notification to MTP (Media Transfer Protocol).
Probably obvious to people who use ADB on a regular basis but I'm too embarrassed to say how long it took me to work this out.