Otherwise, for next time or other people, there is another possibility to get a refurbished (or new one) phone directly with an OpenOS, including a FP3 : it’s « iodé » from Toulouse, in France https://iode.tech/en/.
Interesting.
Just for clarification:
The Fairphones (3/3+) are sold new only, while the refurbished ones are made by Samsung or Sony.
If one should wonder about the higer price (469,- for the FP3 and 519,- for the FP3+), they do come with the modular earphones. They were sold by Fairphone and resellers between 35,- and 50,- Euro; but they are no longer available except in this package it seems, though Fairphone still sells the cable as a replacement.
Still this doesn’t make up for the higher price; but the work to develop, install a new or modify the OS has to be paid for as well.