Granted, I didn’t look at the type of pc, so I didn’t know it was a mac mini, no. I just glanced over the specs, and what I said still stands, so:
When buying a new pc, go for your parts + gpu or better.
It’s not like what I said was “Add a gpu to that PC” even though it was implied. I was simply pointing out where the problem in the build is. 
Honestly, even though mac gaming/design is a thing, according to steam hardware surveys, it’s not really. 4% mac users on steam vs 95% windows users, So you should develop on windows, if you want to test similar to the people that would most likely be buying your game.
If you want an added giggle, guess how many people use linux on steam. 