Procreate app
Drat it. Seems like procreate is only available for mobile/iPad
Don’t know what your budget is but I’d probably be looking at a used iPad 6 and Pencil or iPad Pro and Pencil.
Using your existing iMac as computing power then there are drawing tablet graphics monitors options such as XP-pen and Huion. I’d still choose the iPad + Pencil ( 6th generation onwards) route just because for the budget it’s a more portable all in one option and Procreate is such a good app.
If content to draw off-screen on a graphics tablet then there are lots to choose from. Huion H420 USB is an example of a budget option
Software would most likely be something like Corel, Photoshop, Gimp etc. Maybe Artrage?