I've been working on this map for a few days now.
Coast traced in Inkscape. Lines around the coast done in Inkscape this time too. The outset path function is kind of buggy. On some steps it would connect points that were nowhere near each other, giving you black lines across the picture.
Mountains added in GIMP. These are a couple of brushes I made by tracing mountains off a picture of an antique map. I added more images to the larger brush this time so I wouldn't have as many repeats. But now it looks like I used a slightly larger brush on the first ones. Oops. Also, the large mountains looked a little oversized on this map so I was using the brush at 75% but the smaller brush at full size---so there's line weight variations all over this. I'm hoping it's not noticeable once everything's colored.
Rivers added in Inkscape, using the "shape: triangle out" and "shape: from clipboard" options on the pencil tool. I hadn't tried this before. Results are MUCH nicer than my hand-drawn attempts.
On the longer rivers especially I got the best results using not a triangle as the model shape but a sort of pentagon only tapering only along 40% of its length.
I imported the rivers into GIMP to clean them up where tributaries met and where they meet the coast. Hm. Now I've been playing around with it some more, and it looks like if I'd just set a fill color on everything, I could have used "Union" to join branches and "Difference" to join rivers to the coast.
At this point, I decided I didn't want to commit to placing cities and countries just yet. So this is just a physical map. I slapped some labels on in Inkscape. I'm planning to go back and fiddle with this. Something's not working for me; I'm not sure if it's the font or what.
So that's where I am now on the lineart. Today I moved on to coloring. Picture #2 is me messing around. For a while there I was leaning toward ditching the inked mountains and redoing them all in a painted style (you can also see me trying to figure out how to draw forests). But I also like the look you can see on the southern continent with the strong inked lines just colored in. Also, it's much faster. So that's what I'm going with.