I used it for a while and right up to the point I actually set it up to give it a go, I'd never even heard of it before. Definitely feels like it flies under the radar.
I loved the idea behind it, but a few points ended up sticking out so I ended up dropping it at some point. Namely, I didn't like the markdown editor much, plus it was very awkward to use on mobile (which, granted, is an issue with most competitors). I also don't like how it's dabatase based, vastly prefer using local markdown files. Plus, it's more of a personal thing but I came to prefer graph based implementations better than hierarchical ones. Still, really impressive project and I very much appreciate that it's open source and fully self hostable, not much in the way of competition there when it comes to second brain alternatives.
After exploring a few options, I've ended up on Logseq. Shame that one isn't self hostable, not fully anyway, since last I checked you still need to open a local folder even if you do host it yourself.
I gotta say, upon closer inspection Yunohost looks way more elegant and complete a solution than I was picturing. Figured it'd mostly be premade apps ready to install but there's also built-in LDAP + email, let's encrypt certificates, integrated security features, the list goes on and on. If the execution is even remotely as smooth as the documentation suggests, Yunohost sounds great!