For some reason rendering the hair ‘normally’ (i.e. without Freestyle) poses absolutely no problem (1:27 minutes render time on my 2070) but the moment I try to render it with Freestlye the picture won’t render at all.
So as a quick fix I rendered the image twice, overlayed the regular one on top of the Freestyle version and lasso-selected the hair, reverted the selection and deleted everything else. Talk about hacky.
Edit: I managed to fix this problem now by making the hair solid colour instead of alpha-transparent (doesn’t matter for comic hair anyway) and after that failed to work I went ahead and deleted half the hair. I suspect the line-renderer has problems calculating which of the one-million-and-twenty-seven hair strands needs to be rendered and which not. Anyway, it’s done now!
As always here’s a list of models I used, a big thanks to anyone on this list for being awesome and sharing your models!