Routing through custom KML

Hello!

I set up a local GraphHopper instance in my laptop and i have no particular problems making it work.
I’m trying to find a way to use GraphHopper routing algorithm on a custom KML i have, but I’m a bit lost. The most obvious path would be to convert my KML to an OSM PBF file, but I’m hitting walls with every library or tool i try to use.

Could anyone give me a tip or where to head? Is this even a feasible task in GraphHopper?

Thank you all in advance!