Sorry about your motherboard.
Just FYI: The FP1 was never modular. The FP2 is the first ever modular smartphone.
You can try your luck at the FP1 #marketplace::tag. Either try and find someone who sells a FP1 for scrap parts or do so yourself and let your working parts give new life to someone else’s FP1.
Or you can find a repair shop with FP1 experience. E.g. if it’s the USB port that’s broken many shops can microsolder a new one on the motherboard.