I'd like to encourage you to check out Vrite as a whole. I'm actively working on this to make it better for documentation and knowledge base management. Good UI and UX are among my top priorities.

There's already Kanban for better management of content production process and I'd say the editor is comparable to Outline. Other views and more editor features are on the way.

Still, as I'm updating it almost daily, self-hosting isn't easy right now. I plan to have a stable version sometime in Q3 of this year, with self-hosting and more features so keep an eye out on that if you're interested.

I went down that rabbit hole as well, and I also settled on Outline for our business. We haven't widely deployed it yet, but it's been working great during our limited testing. It is sorely missing robust embeds, however!