I started using manjaro today, I have version 20.02 with GNOME, and when I want to show my screen in apps like discord, I cannot transmit it completely, only the cursor appears and the computer becomes very slow but I can transmit a specific application.
Thank you very much my processor is the i5-3230m with intel 4000 graphics, a hp elitebook 8470p laptop.
I think you are in a Wayland session,type in the terminal
and if it say Wayland,then logout,when you are in the user select screen,search for a setting icon and change Wayland to X11,i don’t know if it like that i don’t use GNOME.
Screensharing with wayland requires using pipewire. You need to set it up, and not all apps support it yet. For an example chromium does, but I’m not sure about our build of Firefox.