Firefox menu opens when changing keyboard layouts (Alt + Shift, Gnome)

Hey,
I just did a fresh install of arch and gnome and for some reason when I press alt + shift to change keyboard layouts both firefox and thunderbird’s menus get triggered and this is super annoying. I am pretty sure I didn’t have this problem on my xfce install so I am wondering where’s this coming from. I guess I could disable the alt key in firefox and thunderbird but that’s more of a hack rather than a fix. The big issue is that for some reason firefox/thunderbird doesn’t recognize that ‘alt’ != ‘alt+shift’.
Any ideas? Thanks.

I have Firefox 84.0.1 on Manjaro Gnome and don’t encounter this problem. Hitting alt and nothing else triggers the menubar, but holding alt + any other key does execute the key combination and does not trigger the menubar.
I do not have any experience with problems in the UI but as a simple first step, have you tried if this is an issue with your keyboard and tried to replace this with another one?

Well if it were a keyboard issue then ‘alt+shift’ wouldn’t work or wouldn’t work consistently. Also I used the same keyboard on xfce without issue. There is some limited possibility that it could’ve broken just now, but I doubt it. I could test it on a different pc, but I don’t think it’s the issues since I think I’ve had this bug before but I can’t recall how I fixed it.

make sure that you have the right keyboard layout configured in that install. I do not have this issue and I switch between French input and Japanese input using the standard 104Key US layout keyboard. My IME switcher is set to use the LShift + Super(Windows) Key, though. Alt Shift is an odd trigger. MS Windows defaults to Shift + Spacebar.

Try setting it to alt+shift and see if you have this problem. The shift button doesn’t trigger anything in Firefox so that doesn’t help me. I don’t remember why I use Alt+shift but I am pretty sure it used to be default somewhere back in the days. From what I see it doesn’t have anything to do with my layout because even when I remove keyboard layouts it still behaves the same way.

Interesting. I will try when I get home.

Are you using Wayland or Xorg.

Wayland

So I switch to ALT + Shift and I am not having that issue. I find this very strange. Does not happen in Debian Unstable or in ArchLinux. Running Gnome3 with Wayland.

Did you take a look in your keyboard shortcuts to see if anything else was linked to ALT+SHIFT, like the meta (context) menu?

This problem only occurs in Mozilla products as far as I can see. LibreOffice doesn’t have this problem. Gedit doesn’t have this problem etc.

Yeah. That is extremely strange. I would suggest reinstalling libinput, locales, and remove and re-add your input sources (settings -> region & language -> input sources).

What is even more strange is that alt+a doesn’t trigger the menu for me, only alt+shift. I am wondering if this is somehow related to gnome tweak tool.

That could actually be a possibility if you are running some non-standard tweaks/plugins.

Big discovery. I disabled the alt+shift tweak in gnome tweak tools and now alt+shift doesn’t trigger the alt menu any longer. The culprit is tweak tools. I guess I could enable alt + shift using an alternative to tweak tools, but I might use this opportunity to learn to change layouts with special + space.

Awesome. I am glad it worked out. If you could mark you last post as the solution, it may help someone else in the future