The search engine does indeed seem to be fully custom - the results for niche topics are quite bad, but that at least means it's not a Bing frontend, so it's forgivable. Although I wonder why the authors decided to go 100% custom instead of (partially?) reusing https://github.com/MarginaliaSearch/MarginaliaSearch for some of the core engine.

On an unrelated note: why do some people use LLMs to write all the text in their projects? As an example: https://xonaly.com/how-it-works - it's obvious that the text here is LLM-written, but I genuinely don't understand why. It's one of the pages linked directly from the home page, so it's quite important. At least personally, I always get very suspicious of any project that doesn't even bother to have some human-written content. (I know the whole website clearly looks LLM-authored, but I feel like it's not hard to add some human touch)

Don't get me wrong, I use LLMs myself quite a lot, but I try to always interact with others in my own words. In rare cases where I need to paste some output from an LLM, I always leave a note about it being AI-written.

Oh, and another funny tidbit I just found: https://xonaly.com/is-xonaly-legit/ repeats the same facts a lot. Ctrl+F "Canad", "independent": 10 results, "search engine": 17 results.