There is an open source for Evernote

"I have switched to joplin from evernote and I am using webdav on synology NAS to synchronize notes. It is open source and also self hosted and works on all platforms without problem. I also share notes with my wife. We use it for planning and shopping lists and it works really great. It has some basic conflict resolution which is usable for two people. Joplin uses sqlite as storage but you can export collection to md files and there is backup plugin which does that periodically. Also you can setup external editor. I am editing notes in neovim and joplin is just for viewing."