There's a location on the frozen guy to investigate and realize that 3 parts had been removed. making those activated on the map, find them and install them in different locations on the tall neck, then activating the dude at another port.

Very early in the game, once I climbed the rocks at Grave-Hoard, a Banuk girl Yariki enabled the Frozen Wilds quest. And to think I was led to believe you had to first play the main game!

........

I soon realize that the game is basically scripted. All main quests have to be followed in order; interact with someone to end the current main quest, they mention someplace that starts a new main quest, etc. I'm going to be much older before the game ends for me!

You don't have to play the main game first, and there is even some dialogue added towards the ending of the main story to acknowledge the fact that the stuff in Frozen Wilds has already happened. You could say that some of the items you get in the DLC make the rest of the game too easy, though.

Agreed.

In my current (and 2nd) playthru, my "Game Completion" stats are 48.60% for the "main" game, and 43.97% for TFW - and I could keep going in TFW if desired, leaving more "main" game until later.

As far as the "main quests", my experience is that it branches into more than one path - and you can follow the paths separately as desired. Not to mention - most RPG's I've played have a "main quest line" that is somewhat linear. HZD has plenty of "side quests", some of which also branch. So.. not sure the issue there.