I honestly don't pay that much attention, but they do have a decent list of potential search sources, so it's not something they're lazy about.
Additionally, this new search site (tuxdex.com) appears to just be a private/anonymous version of their existing search site (websearchengine.net) - although websearchengine.net isn't listed as a source for SearXNG either.
I was hoping to be able to use some esoteric ones, but that doesn't seem possible, unless I've overlooked something.
Being able to aggregate a couple of these up-and-coming engines with result reduplication sounds really neat.