I agree: plain text is after all, easier to manage.
Personally, I've used Joplin [0] some months ago, and Im using QOwnNotes [1] now. Both are open source, cross platform, and can synchronize with Nextcloud. QOwnNotes may feel a bit faster since its written in Qt/C++ (Joplin is an Electron app).
However, I still find hard to write tables in Markdown manually.