As promised:
Update (9/4/22)
Digitized Comics Unavailable on DCUI - DC/WildStorm
Removals:
- Batman Versus Predator
- Batman Versus Predator II
- Batman/Hellboy/Starman
- Batman/Predator III
- Ghost/Batgirl
- Superman vs. Predator
- Superman vs. The Terminator: Fight for the Future
- Wonder Woman/Conan
DC Comics/Dark Horse: Batman vs. Predator, DC Comics/Dark Horse Comics: Justice League Vol. 1, and Wonder Woman/Conan have been pulled from digital sale and distribution (meaning they’ve also been removed from hoopla) due to rights issues. 
The only two remaining DC/Dark Horse/Aliens/Predator crossover collections available digitally are DC Comics/Dark Horse: Superman and Dark Horse Comics/DC Comics: Justice League Vol. 2 (though I suspect that these two will be pulled themselves at some point in the future, so get 'em while you can!).