It wildly varies. At the beginning of my first comic a few years ago I was basically treating it like a second part-to-full time job, but I couldn't maintain that very well.
Nowadays it depends on the day and what I have going on.
Mondays usually 0 drawing because I do a game stream after work.
Tuesdays I try to spend a couple hours if possible but I don't always feel like it.
Wednesdays is Art stream, so min 2 hours, sometimes longer.
Thursday I play D&D with friends so usually no drawing.
Fridays are wild cards, I try to get a few hours of drawing in like Tuesdays but don't always feel like it.
Saturday I do another art stream, so min 2 hours then and usually a few more hours later after a break.
And sundays have been highly variable lately- My family has been requesting my help with various things a lot lately on the weekends, so my sundays have mostly been completely spent on that and little-to-no drawing gets done then either
So the short answer, I guess, is 0-4 hours per day, averaging at 2 when I do work on it and 0 when I don't. Notably I work full time outside of these activities so that's where most of my time goes.