I have 1.8.12 IDE installed and I can upload sketches from the IDE to an Arduino UNO rev3.
I'm trying to set up a new Arduino DUE. First the DUE was not on the board list. From this site I read that the DUE could be added by running the Board Manager utility. I 'installed' the DUE and now it appears in a separate box at the bottom and there are 3 choices with only two being active. Arduino DUE (Native USB Port) and Arduino DUE (Programming Port)
In the picture below it shows the board being an UNO with a port connection. When I select from the DUE box at the bottom then the port selections goes dead grey. I have exhausted my limited knowledge.