Is Arthur Dent the hero? I imbibed him more as a passive vessel to experience the absurdity of Douglas Adams universe. But it’s been a while since I read it, but from memory all the situations are so absurd that I never felt myself yelling at the hero to make a more logical, or “herioc” decision because there wasn’t really a lot of sense in that sort of thing

I think so. He's more storm-tossed survivor than Moses parting the waves, but he makes the best of the endless shit he's dumped into and preserves his sense of self throughout. I think he responds heroically, far more than he fixes anything external. For example he finds himself marooned on a strange planet and sets up a Perfectly Normal Beast sandwich shop, living very comfortably for a while.

For what is he fighting against? Nothing really, he's just adrift in the universe. There's no antagonist beyond existence itself and his own circumstances. He faces off against both quite effectively.