Serif Affinity Photo, Designer and Publisher are all great - I've been a happy professional user for a number of years: they are good enough for my design / origination / artworking / printing work. However, I've not had any success in getting them to run on Wine / Crossover, so I still have to use a win10 VM for them. If you've figured out how to use any of the Affinity products under Linux, I'd be seriously interested to know how.
In the meantime, for anyone looking for Adobe CS6 replacements to run on Linux, i can recommend photoshop+illustrator CS6 be replaced with the usual combo of gimp (not ideal, but it does the job) + inkscape (better than Illustrator for what I need)
The big issue I see repeatedly for people who wish to move off CS6 is a replacement for InDesign. Until last year, I couldn’t find a decent viable alternative.
I spend most of my working time in InDesign, so finding a Linux alternative has been critical. And after 15 years of looking I've finally found one: VivaDesigner - the UI might not be as polished as one might like, but the support team are very responsive, and VivaDesigner can produce large documents as PDF files preflighted to PDF-X/4, and that’s definitely good enough for me. Now all I have to do is finish moving client projects from InDesign to VivaDesigner (the .IDML import in VivaDesigner is helping massively with that).
If anyone needs an InDesign replacement, take a good look at VivaDesigner.