Krita or Glimpse might be the answer here
>"Can't be any more than 20 odd years that we have been hearing that same phrase !!"
Well, there is a reason, even if it is just obstiance.
I am not a graphical artist and so I am unable to professionally assess different graphics apps claims but I do know the following:
1.) Artists have been on the GIMP team's back for ages about making GIMP nicer for creators to use but they have refused every time stating that GIMP is, and only ever will be, an image MANIPULATION tool and not an image creation tool! Which is why, to date, no Photoshop like app has ever appeared for Linux. The GIMP have always insisted they will never attempt to go the Photoshop route.
2.) There is, however a new kid on the block - Krita. This is taking the exact opposite approach to GIMP and IS a graphical editing tool with input from artists and designed for the CREATION of images! Any budding Photoshop equivalent in Linux is likely to be found here rather than GIMP.
Most Linux users appear to be completely unaware of Krita but it's development has been fast! Indeed GIMP has slowed in terms of feature addition, almost to the point of stalling, Krita has a new release with new features every six months as part of the base KDE app install program!
However, Krita is a KDE/QT app which, with Mint having gone all in with the GTK route would not be suitable as an app in the default Mint install.
Personally, I find the GIMP interface easier to handle but I am not a graphical artist in any way whatsoever and so cannot really comment on the workflow or features.
3.) GIMP has now forked due to naming controversy (of all things!) and now we have 'Glimpse.' At this stage Glimpse is functionally identical to GIMP but there is now room for a new team to develop the code with more of an open ear to artists and Glimpse may yet become what a lot of users have wanted GIMP to be... forever.