I'm using mkdocs with the material plugins [1]. I'm running it mainly for a Blockchain Education site for my labs from my course, which seems to be fine [2].
I did a fair amount of customization though, so I am running all this as mkdocs plugins, not directly from the materials project.
Another +1 from me for mkdocs and mkdocs-material (and I'm also a supporter of squidfunk). I use it for lab exercises[1] as part of my online courses (deployed onto Netlify). It just works and looks good.
Another happy user of mkdocs, also really like gitbook. If I had to choose something for people who didn't like git/plaintext and wanted richer embeds, I think I'd suggest Notion.
+1000 for the "Material for MkDocs" project by squidfunk - we (Ritza.co) do documentation for various companies and we've strongly encouraged them to all switch to this since we found it. Fast, beautiful, simple.
The free version is really nice but also very happy to pay for the 'insiders' version via GitHub donations.
[1] https://moretestable.com