Currently I’m using Joplin with Syncthing-backed file system synchronization. I’m pretty pleased with it, as I do like tagging- and Markdown-based systems.
I plan to upgrade to server-based synchronization, but before doing that, however, I wanted to see what other people are using.
Edit: So far I see a slight favor towards Joplin and Logseq, but I totally didn’t expect (and appreciate) getting so many different answers.
Then Logseq. It’s an outliner (each line can be it’s own…thing…), but it’s open source and a direct competitor of Obsidian. In fact, I was ambivalent between the two when I first started with online note-taking.
That looks very interesting, mostly because it’s so different. I’ll have to take a closer look later.