This app has a very similar look and feel to it as Obsidian, and also works in Markdown format. And although Obsidian has a kitchen sink full of community plugins, this app is a lot simpler, but it is proper open-source software.
I also like that it has a toolbar with all the usual shortcuts like bold, italics, underline, headings, bullets, etc as many people do like that ease of use, instead of only having to remember Markdown codes.
Very importantly for note taking, it does have easy-to-use tags that will help connect all your related notes. If you do need to sync your notes between devices, you could use something like Syncthing that will do that privately and directly between your devices, without any server required.