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.
Emacs with org mode. It has so many feature hooked into so many other things such as time management, calendar, email, jupyter. Hard to switch.