I did send letters to Nival and Ubisoft about H5 source a few years back.
Nival responded but they could not do anything because Ubisoft holds the rights.
Ubisoft did not respond but I am not sure if I sent the mail to the correct place.
If you are going to send a community request to Ubi, count me in!
Perhaps Ubisoft is interested in the double standards in their favor? For example, how they handled Warcraft 3 Reforged, where everything created through their map editor belongs to Blizzard. Did you consider this when sending your letter?