> I had no problems when performing the on-line upgrade with Ubuntu/Mate 17.10 to 18.04. 

On closer inspection of my Ubuntu/Mate system tray it is missing some icons. ie. Network connection, battery status, bluetooth.

This Ubuntu-Mate 18.04.00 bug has been a reported...

...Maybe there is some merit in waiting until 18.04.01 is released before upgrading.

cheers,

Ian.