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.
QOwnNotes (had to look up the exact name as it’s the stupidest app name ever). but compared to joplin it’s lighter, faster, simpler (no database but individual .md files and folders) and works well enough with syncthing.