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.
For long-term, permanent notes, I’m using Obsidian with Nextcloud and FolderSync Pro (which I also use for backing up some Android stuff to my Nextcloud).
For quick, easy notes while on the go (or that I need quick access to while out and about), I use Memos, which is more of a Google Keep replacement.