A few weeks ago I went through the process of looking into every foss note taking app I could.
Problem with Standard notes (the free version) is that its extremely basic and kind of useless. It doesn't have richtext editing, check lists, or even Markdown. Its only a plain text editor. Paid plan is way expensive.
I tried Joplin. It felt kind of over complicated and its essentially just Markdown. Well, so is Quillpad, but Quillpad is just so much cleaner to look at. The Markdown in Joplin however might be more complete and you can do added plugins for extra Markdown features (not sure about the android app though). I didn't try Obsidian but its very similar to Joplin.
So I'd say If you want a more complex and sophisticated option with more features go for Joplin or Obsidian. If you want a simpler option go for Quillpad or Notally. Quillpad is the middle ground between Joplin/Obsidian and Notally.
Notally is very basic rich text format. Notally has no undo/redo buttons.
wojon Please note that Notally seems to have a bug that can, as far as I understand it, lead to the loss of your notes in certain cases. Also, I wonder why the github repo doesn't have the option to submit issues. Seems strange.
spiral I tested out Notally for a few weeks when I first started using GoS (August 2022) and found that it most definitely deleted notes. This happened multiple times.
Notally had this problem where you could accidentally swipe on your list items and they would get deleted with no way to undo. This has been fixed. It now also has a recycle bin so files you delete can be brought back. Is this what you are talking about?