A recent news informs us that the open source program Krita has reached a new release with version 5.1.3 .
From my experience I can say that it is the best program that includes enough features for those who want to use 2D graphics. From simple tasks, simple modifications, painting or animation, this program does it all.
You can se how you can set your brushes from the youtube official channel.
You can add your name and contribute to this open-source app that works on multiple operating systems with a contribution on their official page.
You can find more information about what fixes and changes have appeared on the official website.