The Dark Island is exclusive community-made level pack to Gold Edition, although it was included into the Gold Edition by Croteam, so it is some kind of "official" thing here, therefore IMO there should be a speedrun sub-category/leaderboards of this obscure episode/levels.

More info: Serious Sam: Gold Edition | Serious Sam Wiki | Fandom

I just wanted to remind that this ultra-obscure content actually exists and moreover IS chosen by Croteam. It might be a good thing to put to the miscellaneous section or category extensions or to expand the IL-leaderboards list.

Example of the runs:

Yeah. I really want to running this

I really think it's worth it, it would be cool if added it