The ancestral high elf, nord and orc motifs drop in treasure chests, from treasure maps. (they may drop in chests that aren't official treasure maps, but can't confirm that) Each piece drops from a specific treasure map, so keep track of which ones you get leads from, because you will get the exact same leads from it the second time around. I'm a bit surprised that none of the data miners have put out a list of exactly which motives drop from exactly which treasure map. It's very specific which map will drop which motif leads.

If you are trying to get these specific motifs, only purchase maps for the main faction zones for EP, AD and DC. I did not keep track, so this example might be inaccurate, but it gets the idea across. I think EP zone maps drop nord, AD zone maps drop high elf, and DC maps drop orc. (that might be the wrong faction to style pairing, but it shows the pattern to follow if you have all of one motif style already. If you have all the AD, DC or EP pages, stop buying the maps for that faction, because you will only get duplicates)