I'd also recommend Gitbook. They've improved their search features recently and I'd say they're on a similar level to Notion.
We used it for our company wiki. Wanted to use Notion but for 500 users the Notion quote came out 15x more expensive so it was a no-brainer!
I'd stopped using it because it was too easy to outgrow the free plan. Now with unlimited pages I'll give it another shot but I'm still not sold on its benefits vs storing all my notes locally in plain markdown files.