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.
I also really liked Google Keep. Carnet was at one point a decent drop-in replacement on Android+Nextcloud, but it got progressively bitrotted over time and now I just use Nextcloud Notes until I find something better.