First off let me say I am using Arch Linux (as opposed to ubuntu) but generally speaking there will be people who want to use your program that are not using ubuntu or a ubuntu based system, so when I installed the software I got a "command not found" error after running the .run file for apt-get, the software luckily did install successfully but failed to fetch it's dependencies since I use a different package manager.
Supporting all the package managers would of course be an unreasonable request, however the problem that arises is that I now had a paintstorm installation with missing dependencies and worse, I did not know what dependencies it has. I solved this by trying to run the program, getting an error for some missing library files, and downloading the corresponding packages to get those library files. Luckily there were only 3 I was missing (Glew, Glut and libcurl-gnutls) so it didn't take long.
To make the software more approachable for people who are not using Ubuntu, you should include a dependency list on the download page or just in here.
The second issue I had was the version of GLEW that is required, Paintstorm seeks libGLEW.so.1.13 however arch linux which I was using has a more recent version of GLEW, or libGLEW.so.2.0; to solve this issue I symlinked (ln -s) libGLEW.so.2.0 to libGLEW.so.1.13 which solved the issue. To tell the truth I don't know the best way to deal with library version discrepencies between distributions, but there should be some way to make it more flexible and use the newer version instead if the old version is missing. I hope (that is also what we call future-proofing I guess )
The third issue which is probably the easiest to fix is the location of that the location of the executable is not in /usr/bin/ and what this means for linux is that the paintstorm program won't be added to the BASH command list as an executable software. (The executable if I remember correctly is /usr/share/paintstorm/Paintstorm) while the idealized solution for this problem is that executables should be in /usr/bin and the rest of the software's files should be spread around in some (organized) chaotic mess in the various /usr/ subdirectories, I think the most painless and sensible way to solve this issue is to simply symlink the executable to /usr/bin/ so, basically after installing the program just make it run this command: ln -s /usr/share/paintstorm/Paintstorm /usr/bin/paintstorm and this issue is solved.
It's typically expected of software in linux to be executable by typing their name (or some version of their name) into a command terminal, so the third issue is bigger than it would seem to someone who doesn't regularly use linux. For many users not having the executable in /usr/bin means they need to search for the install directory, which, while common as hell under windows and not a problem at all, is a confusing task under linux because you never know where a developer who is not an expert linux user might have decided to throw all his files (most commonly they tend to throw it under /opt/ somewhere, but I think /usr/share is as good as anything so I'm not gonna comment on that, I don't need my software to be perfectly organized the 'linux' way, I just need it to work.)
And that's it for my issues on Linux so far at a glance. As far as I managed to test in a handful of minutes after this ordeal, the software runs beautifully, even on GLEW 2.0. (Wonder if it's fully backwards compatible with 1.13) so far I've been nothing but impressed with the Linux version, you're doing a good job here, although I really do hope you will listen to my request to add Libinput support sooner rather than later since it's sorta my only hope to draw on paintstorm on my main workstation considering I have a non-wacom tablet, so it's a really important feature to me. After you add it I can do full time linux beta testing for you hehe, as you may have noticed you can count on me to report things. I should probably be more diligent in sharing my hardware/OS info though for added clarity.
I can't wait to see paintstorm grow more.