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.
Unsaved n++ tabs
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.
Joplin. Obsidian is not open source, doesn’t have native self hosting and it gets complicated. Joplin is very simple and just works. Although, it stores the notes in a hashed database, so you can’t edit raw files without Joplin client
Problem with Joplin: The raw files are randomly named so you can’t easily find a specific note
Honorable mentions for hedgedock.
Depending on how deep you are into the technology, Emacs orgmode and neovim with neorg are probably the highest quality ones.
I personally can’t get away from obsidian, it’s just too good. Stores just as simple directories of markdown files, tons of good extensions, easily kntegratable with other syncing options, and supports tags.
Obsidian. I know it’s not open source, but it just felt right.