Juhele

Regarding some already working commercial paid linux apps:
Autodesk Eagle
https://www.autodesk.com/products/eagle/free-download?plc=F360&term=1-YEAR&support=ADVANCED&quantity=1
says for linux requirements:
and (just tried) you get *.tar.gz - no particular distribution specified... My colleague is using it on linux machine so could possibly tell me more...
 
SoftMaker Office - for Windows, Mac and Linux
https://www.softmaker.com/en/softmaker-office-download
 
Lightworks
https://www.lwks.com
 
I am also using paid VueScan scanning software in linux and was quite satisfied with Kolor Autopano Giga photo stitching app (unfortunately discontinued and later acquired by GoPro as I remember)
 
So I would say that paying users expect you to manage compatibility for mainstream 64bit distributions - DEB packages for Ubuntu and its flavors / Debian and RPM packages for OpenSUSE / Fedora. There is no need to worry about usability in every obscure distribution.  If you want to have a multimedia linux workstation then you choose mainstream.
PS: hope the links above are not considered advertising as the mentioned apps have quite different field of use than Affinity apps

Definitely. Affinity Designer on linux would be probably the biggest event for the linux users. There are several raster graphics editors but there is a big gap in vector graphics. Yeah, there is Inkscape but unfortunately is has issues and suffering lags even on powerful PCs... 
And just to add when people here compare Affinity with Adobe - one of the big advantages at least for small companies and home users in that you still have "normal" license and not subscription. It is often not problem to get money to buy software but just as one-time payment and subscription is not possible for formal reasons.
I know several (Windows) users dropping Adobe and replacing it with Affinity because Adobe being too expensive with the subscription. I think there would be much more new users with Linux version available.

I do not think it is necessary to complicate things at the beginning. Some time I bought AutoPano Giga from Kolor which is advanced panorama stitching tool. It was also available for linux but as I know nobody of the commercial companies cares about some "exotic" distros and most users would probably have some mainstream distros. 
It is common to support 64bit linux systems using DEB packages (e.g. Debian / Ubuntu) and RPM ones (Red Hat Enterprise / CentOS / Suse / OpenSuse) which are also use in companies / institutions / studios - you can check how for example Microsoft does it with Skype or SoftMaker with Softmaker Office for linux.
Besides, there are also the universal package solutions and things like appimage (Avidemux uses it for example).

I do not think it is necessary to complicate things at the beginning. Some time I bought AutoPano Giga from Kolor which is advanced panorama stitching tool. It was also available for linux but as I know nobody of the commercial companies cares about some "exotic" distros and most users would probably have some mainstream distros. 
It is common to support 64bit linux systems using DEB packages (e.g. Debian / Ubuntu) and RPM ones (Red Hat Enterprise / CentOS / Suse / OpenSuse) which are also use in companies / institutions / studios - you can check how for example Microsoft does it with Skype or SoftMaker with Softmaker Office for linux.
Besides, there are also the universal package solutions and things like appimage (Avidemux uses it for example).