In Ubuntu 20.04 with GNOME flashback, there is no menu bar in LibreOffice (the one with File, View etc.). I read somewhere on the Net that the issue is related to libreoffice-gtk3 package, and uninstalling it brings the menu back. I tried it – it indeed brings the menu back, but the menu is very ugly, as it has a "raw" X application look, completely unrelated to the currently set GNOME theme.
How to bring the menus back in LO while keeping the system theme?
It looks that Ubuntu is getting worse with every release. I started with Ubuntu 10.04 where everything worked just perfectly "out of the box". With each new release I install, there is more and more trivial things that are not working and require much effort to fix.
EDIT: Just found another LibreOffice issue – help does not work. How many more will there be? Starting to think about reverting to Ubuntu 18.04…