Dual booting older (2011) MBP into Windows and Linux (not macOS)
I read your this article. Follow the steps outlined in the article with these adjustments.  I'd set up three partitions instead of four: macOS, swap and Windows. I'd adjust the macOS partition to the size you want to for linux. I'd install linux over the top of the macOS partition. 

I've set up a triple boot system before but I haven't tried this procedure. Good luck.