You can try removing search engines that fail or reducing their timeout setting to something faster than the default of a few seconds.
SearXNG is fast, its mostly the code that triggers the searches. Because, my daily is chatgpt, i still did not try to tweak it.
I haven't needed to tweak mine for similar reasons, but I'm surprised to hear that the "code that triggers the searches" is slow. Are you referring to something in Open WebUI?