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 use Memos, but I didn’t like the MoeMemos app when I tried it. Text to small and horrible theme. I installed a shortcut to the Web client and it works great. I usually want dedicated mobile apps for the stuff I use, but Memos is so simple, I don’t think a mobile app is needed.