idk if it counts as a program, but i like using kleki.com! free website and id like to think it's also user friendly (or maybe that's bc ive been using it for years idk), it gets updated frequently too :3 creator makes tutorials on how to work it on yt as well!!

clip studio paint hmm there might be some others but its just not compatible with the computer i have

krita!

Krita. it's free :3

Ive heard Krita is a little bit difficult to get used to but yeah Krita Also FireAlpaca! theyre both free