I have reluctantly been using obsidian after trying every floss alternative. It is portable, easy to start with and there is a rich plugin community. Unlike joplin, the closest floss competitor, it actually stores files in plain markdown so if you need to access them through another tool you can. Obsidian adheres to the unix philosophy better than joplin. :(

They are both electron which sucks but at least with obsidian you do not have to be running the application all the time because of the plain markdown thing.