I've installed The White March and have the patch 2.01 through GOG Galaxy. I am already questing inside Defiance Bay (so clearly Act 2) but there is no sign that I can start the main quest for WM.
Who and how does one trigger the quest line?

Thanks.

You need to go through Woedica's temple to trigger White March. If you did and it didn't trigger make sure you have White March enabled inside Galaxy (in my case it was off by default and I had to select it manually).

Thanks.
I have already found this info on Obsidian forum. Right now I am inside the said temple, so in a short while I will know if the quests are triggered or not :)

EDIT: Confirmed. I've got the quest.