I'm beginning to think that I have to shoot and develop a negative specifically for salt prints. I'm wondering negatives for salt prints can be printed on silver gelatin paper.
Yes, you will and no, you usually can't. Salt prints are very long scale and want a high contrast negative. A good place to start is with ISO 100 speed film, normal exposure, and double development time. That ought to get you within spitting distance of the ballpark.
Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming– “Wow! What a Ride!”
This negative prints normally on silver gelatin (grade 2 or with no filter on VC paper), yet made a salt print just fine -- and it was a lucky first-time-with-salt-printing print, so I have no idea if I can repeat it.
It was double-coated (on Crane's Cover), with no contrast agent added.
At least with LF landscape, a bad day of photography can still be a good day of exercise.