Under "signals" tab the third field from top to bottom should give you LTE band.
If you are on 4g+ it will give 2 bands.
I don't know if it will display downstream channel width (if its 10MHz it's cat4 LTE, if its 20 MHz or higher its Cat6 or above, i.e. 4G+).
For example, Mi5 supports Cat12 LTE...