I have about 20 artboards in my Photoshop project with many different subjects (3 or 4 artboards for each subject) and I want to separate them (like turn them on and off per group).
So, can i make a group of artboards?
Unfortunately artboards can not be grouped in Photoshop CC 2018. There is a feature request on the Adobe Forum from 3 years ago.
As a workaround you may want to organize your canvas as layer group instead.
Short answer: No.
Artboards act like a top level group, that can have groups and images inside, but can't be grouped themselves
A possible workaround is to name your artboards by subject followed by a number, and arrange them in blocks.
If you want to work on one subject only, and want to be able to find the artboards quickly, you could filter it using the Name filter in the layers panel