Joplin is old but gold in terms of open source not taking. However, I always found the experience to be a bit too clunky even after writing 100s of notes.

Obsidian is much nicer but you gotta set up your own sync or pay. Same basic premise of markdown files on your local file system. I've been enjoying it a lot and written more since switching.

You do not even need to run a dedicated server if for example you already have an owncloud/nextcloud setup, since all clients (desktop and mobile) can sync from a WebDAV folder (among other backends).