Hey Jack, welcome to the community! I personally do 95% of my map illustrations on a tablet. I am currently using an iPad with the Procreate app, which is definitely the best app I have found for drawing. But, if you are using a Samsung I would recommend trying the MediaBang app. That is what I used for quite awhile before I made the switch to my iPad. The one benefit of that app in particular is it allows you to have larger canvases than most of the drawing apps I found for Samsung.

Hope that helps, let me know if you have any follow up questions for me!
- Josh