Affinity products are decent, but they're not free, it's a one time purchase.

There's Krita, which is good, but I really want something that mirrors the traditional tool layout of Photoshop. Both affinity and Krita do their own thing which is tough when you've been using Photoshop for 25 years.

https://vimeo.com/100377108

To repost their comment:

“ In my work, there's constant discussion about which is the best and hottest new design tool to use. I’ve tried many of them, but in the end I still keep coming back to Keynote. It’s easy to learn and use, swapping assets is a breeze (using media placeholder), and most complex animations can be tested with Magic Move (the secret sauce to it all). Producing animations can span a range of fidelities; I can produce all the assets in Keynote, or I can copy out of Illustrator or drag and drop from Sketch (how seamless this works puts a smile on my face every time). As an interaction or visual designer, if you’re not using Keynote to test and bring your work to life, then I think you should start now! At least I hope this little experiment inspires you to try.”

For drawing I would say Krita.