I think what would be interesting is to get everyone who self hosts this do part of the indexing. As in, find some way to split the indexing over self-hosted instances running this search engine. Then make sure “the internet” is divided somewhat reasonably. Kind of what crypto does, but instead producing the indexes instead of nothing.
I can’t come up with just one and this list changes over time a lot for me. But here is a current top 3 for me
Dry the River - Weights and Measures
Tallest Man on Earth - Dark Bird is Home
Elbow - One Day Like This