Also, it seems so random. Like, why are there not one, but two Minotaurs just aimlessly wandering around. And so far from Labyrinth (assuming it's in BG3)?

Anyway, I got to the Underdark by going down the well and then jumping down after the Phase Spider fight. The "angry DM" was like, "Welcome to the Underdark, MFS!!!". Both minotaurs engaged in battle as soon as I landed, immediately TPKing me in one round. After several tries, and one Potion of Giant Strength later, Lae'zel was lucky enough to shove them off the high walk ways, sending them falling a long way down, dealing half or more damage to them. Making them prone and my party having the high ground was just barely enough of an advantage to squeak by for the win.

That encounter is NOT for a level 4 party!