During my brief iPad ownership in ~2013, I used an app called Paper(?). It was a "natural media" type of thing, like the old Fractal Design Painter back in the day (anyone remember the Mac app that came in a paint can?). You had all the brushes, pens, crayons, charcoal, smudgers, etc. and then about 14 gazillion paper/canvas types to choose from. I have no idea if it even exists, but, for what it did, it was pretty awesome. And that was 7-8 years ago, so if it is still around, then it's going to be 7-8 years' worth of more awesome, I'm sure. I'm not really a freeform, artsy/painterly type of drawer, but that app kinda turned me into one. I was drawing the shit out of flowers, leaves, landscapes, sunsets, etc. for a while there.
And no real-world mess/clean up! It was pretty awesome and I felt pretty artistic. I used it on a plane trip once and it caused the cutie-pie/vixen sitting next to me to strike up a "oh wow, that's really amazing...you're very talented!" conversation the entire flight, so it gets extra points for that.
And going strictly by my Mac-based usage, I'd have to say give the two Affinity packages a look...Design and Photo. Design is more the Illustrator, Photo is the Photoshop. Probably not straight-ahead casual drawing apps, but the number of tools and functions, for a one-time price, will put that level of software on your iPad, subscription-free. I'm sure the pixel-based Photos will offer all kinds of freeform drawing tools.
There are quite a few articles from the first half of 2021 that highlight/showcase "the best 15 iPad drawing apps", etc. Do a quick Google and you'll probably fine more info/reviews than you can shake a stick at.