I'm having a similar problem with the new search update--previously I could search "Monsterhearts" and find a number of fan-made products regarding the game, but I've similarly noticed a cutoff to the search results that prevents me from locating any further supplemental material for the game on this site. I'm a bit disappointed pagination won't be added to the search results, as I've found that the previous search system worked well for my intended use of it. This one, not so much...
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as I've found that the previous search system worked well for my intended use of it
There was a cutoff before. I do not understand how this could have worked for you before.
Maybe try switching to physical games, as some of those are released there and some in "other" and some in (computer) games. And if there is no common tag used by these projects, a internet search with site:itch.io topic-of-interest will be better. Itch's search is still optimised for title search. So the projects would have to include your topic in title.
I think the tag page might me a suitable solution for you: https://itch.io/physical-games/tag-monsterhearts