I tried with setting GDK_BACKEND=x11. As long as GDK_BACKEND is set for the new firefox call, when adding a new tab in a terminal it works.
If I set GDK_BACKEND only for the initial firefox call, the subsequent calls in another terminal with GDK_BACKEND unset do not open a new tab, and after a few seconds a window saying that firefox is not responding appears.
I will make firefox run in X11 mode for now. But I would be happy run any experiment that could help solve that issue.
I tried with setting GDK_BACKEND=x11. As long as GDK_BACKEND is set for the new firefox call, when adding a new tab in a terminal it works.
If I set GDK_BACKEND only for the initial firefox call, the subsequent calls in another terminal with GDK_BACKEND unset do not open a new tab, and after a few seconds a window saying that firefox is not responding appears.
I will make firefox run in X11 mode for now. But I would be happy run any experiment that could help solve that issue.