I try to solo the artillery loading when I see it but I know I inevitably get a patrol coming towards me if I take too long, and I'll find enemies will pop in on my location if I'm traveling alone.

If you wanna solo the SEAF artillery, hunt down all the shells and bring them to the loading area BEFORE interacting with the terminal. Some people say that the terminal doesn't impact spawns, but I'm not sure I believe that based on my own personal observations. I feel like artillery terminals act similarly to geological survey terminals, in that they're a scripted enemy spawn event.