I can only relate personal experiences. DiffEq courses (ODE and PDE) were a continuation of the calculus sequence, so it was a logical progression. It certainly wasn’t easy, but it you deeply understand Calc principles (not just the memorized formulas), DE shouldn’t be too bad.
I found Discrete pretty easy - even my D who has studied the topics in her Math Circle found them logical and straightforward.
LA was it’s own animal. From what I recall, performance there didn’t mean much elsewhere. It’s probably built upon for a Math/CS degree, but I don’t recall using it much in future engineering coursework, certainly not DE/Discrete.