Opensource Notes app recommendations?

I'm looking for a notes app. Not a planner (I use a notebook for that), or an app exclusively for reminders (I also have that), just somewhere to capture my thoughts. I've been using google keep for years, but I recently realized it lacks the organizational structure I need to be able to more regularly reference past notes. I was wondering if someone had any recommendations that fit some or all of the following criteria:

* Must have:

* can …

app capture folders google notebook opensource photos privacy recommendations reference thoughts