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.
Node-RED is amazing! I find it strikes such a good balance between usability and user friendliness, been using it for automations alongside Home Assistant for a while. Outside of the usual IoT scenarios, you can also use it kinda like Android's Tasker if you get creative enough, as in for general purpose automation. Closest alternative of sorts I've found for PCs so far.
I remember using it to expose my (dumb) keyboard's RGB lighting as a controllable entity within Home Assistant at some point lol, that was a convoluted setup. Had a Windows PC where Node-RED would call a DIY python script that would then use a library to interface with the keyboard. I then managed to wire that up to HA somehow. Fun little project, for sure.