If you've found a flow that works for you, that's great! I would imagine though that using a Discord server would be a little limiting and awkward when having to copy-paste every post bit by bit? I use the Google Docs app on my phone to do a similar sort of thing, which might be worth checking out if you want to try something different.
The adobe licensing model is actually what pushed me to move to the Affinity suite of programs, as they have really good alternatives to Adobe products that are pay once, keep forever. They have Affinity Photo which I think it a really good alternative to Photoshop and it has all the same sort of tools that I had come accustom to in Photoshop: https://affinity.serif.com/en-gb/photo/. You can also switch seamlessly between AF Publisher and AF Photo to edit the art assets embedded in your layout, which is really cool!
I've also used GIMP before too but I found the whole experience really jarring coming from a long time in Photoshop, as I had to relearn how to do all the basics and the new shortcuts for all of the things I was used to.