It could work, but following the exact instructions on that site probably won't, because they both use some tools or make some assumptions that aren't correct in Mageia. That said, as far as I can tell, the application is in a single RPM package, so you might want to try downloading it manually
http://download.opensuse.org/repositori ... x86_64.rpmand installing it (just open the downloaded file, or run the urpmi qownnotes-19.7.1-1.1.x86_64.rpm command in a terminal). You won't get automatic updates this way, but I can't think of a better solution right now.
If that doesn't work, you could try following the instructions for Building QOwnNotes (you'll probably need to install additional devel packages to compile from source)