Trying to install Lubuntu 18.04 LTS in this Macbook to extend its useful life. Maximum it now has is 10.7 but that is obsolete for internet purposes. I have downloaded the Lubuntu iso but when I burn it to DVD (using my 2010 Mac Mini with Yosemite) the result is a Master Boot Record DVD, and not the desired Partition Map GUID. I suspect I must first convert the iso to dmg but I know nothing of how to do it.

I have also tried creating a USB boot drive. Ubuntu forums describe a procedure using Etcher but again this was a no workie for me.

Anybody with a detailed, easy, tried and tested way? BTW I have no knowledge about navigating through Terminal, much less using the command line.