Two-part epoxy was also tried, which matched the un-threaded holes in strength. So for resin parts you’ll probably be best served by just modeling the threads in CAD and printing them directly.

fiberglass and resin, leaving a gaping hole in the board. He fastened a patch for the hole from some epoxy glue; Araldite is the brand he used, but any two-part epoxy, like JB Weld, should work.