I'm looking at a 2019 Giant TCX Advanced Pro 2 which was sold as a 1x. I have a Shimano 2x groupset laying around and would love this bike as a 2x.
Based on this image from this sold listing, it looks like there's a spare entry into the downtube:
And this review shows a hole behind the seat tube above the BB:
Are my eyes decieving me or could I run gear cable down that and into a front derailleur?