I am new to Ubuntu Mate but have installed & used Ubuntu 16.04 recently. I ran across Ubuntu Mate 16.04 LTS & decided to install it in place of Ubuntu 16.04.
While using Ubuntu 16.04 there was a simple GUI to install to change the boot selection order, screen font & font size, background photo, etc but I can’t figure out how to do this in Ubuntu Mate.
You could also have a look at rEFInd, it’s an alternative to grub which works really well with customization. I don’t customize my bootloader, but I have several friends who have, and they haven’t had any trouble with rEFInd.
Thanks lah7, TextChew & wizd3m. Grub-customizer is the program in Ubuntu I used before & installed without issues. rEFind looks good but went with customizer.