Because I was raised with Photoshop and I was happy with GIMP for maybe 3 years and then another 15 years I wasn't I always tried to find me right alternative. Using wine or vmware (and others) is one way doing it, but having native editor you like is very nice as well. I have these demands on editors, either they offer something interesting and maybe even something Photoshop doesn't have or if you are offer nothing better and just subset of Photoshop features then at least don't have 180 degree different workflow which is not pleasant for me. They need to be multi-platform and run at least on Linux / Windows. These are editors which I find interesting:

• myPaint (which looks simplistic, but is superior in couple aspects to Photoshop and really it's nicely done and very different from Photohop in very good way. There is lot of tasks now which I will attempt only on myPaint, because there is no point trying to do it in Photoshop. Having devices with wacom tablet input helps)
• Krita
• Pinta (which is subset of Photoshop, but ok editor for simple tasks, and you can download plugin to support WebP)

Because Debian 8 is suplying older version of Pinta I wanted to recompile recent one from source. How it's  easy will be shown in few lines. I will ask to install all the dependencies for building older pinta, but looks like the newer pinta has same dependencies so it builds nicely on first attempt. I will configure it to be installed to /opt directory but you can change it. You will have to make links or desktop/menu links manually yourself.

sudo apt-get build-dep pinta

wget https://github.com/PintaProject/Pinta/releases/download/1.6/pinta-1.6.tar.gz

tar xvzf pinta-1.6.tar.gz

cd pinta-1.6/

./configure --prefix=/opt/pinta-16

make

sudo make install

And done. I wanted to share this one not because it's tricky to do, but because I wanted to give example how easy it is to do.