Did you guys knew that Autodesk's Sketchbook is now free to use? While in the past they did offered a free version, that one had very limited capacities to the software, and you had to pay a monthly or yearly subscription in order to use the full version.
But now they are offering the full version to use at no cost, you only need to create an autodesk account in order to unlock it though.
I'm mentioning about this because I had used this program for many years, it's a really good and robust illustration app that's not too hard to learn, and it's one that I do still like to use from time to time.
Link to their site where you can download it sketchbook.com