Firefox drop-down menu (from menu bar) wrongly size on scaled diplay

My windows 10 laptop setup is an external 1920x1080 at 100% zoom and the laptop screen set-up as secondary, at 2560x1440 scaled at 150%. Firefox (79.0 (64-bit)) works fine on the primary (unscaled) display, but on the scaled display all the drop-down menus (extension, but also hamburger from firefox) are too small, and the contents are either not entirely visible (typically for the extensions) or need a scrollbar (like the main firefox menu). I tried to run firefox with extensions disabled but the problem persists. I think this is a Firefox bug. Is it true and if so, how do I report it?