It's currently in early development and I don't know how well it works, but Xournal++ mobile is a thing. Its desktop app is really good, so I'd expect the mobile app to eventually get there aswell.
Edit:
Whoops skipped the drawing part, Xournal++ is more for note-taking. Krita is a good choice for drawing.
It's the full Kira desktop UI and app on Android. Digital pen drawing with pressure sensitivity works without further setup. The pen buttons don't seem to work natively. The version seems to be not the most recent Kira release (is the previous feature release instead).