It used to work before, but now if I hold the alt key in a GTK program, I can’t type any letters.
Using a key other than alt only works if no alt key is chosen as another button for 3rd level.
~ » uname -a
Linux HOSTNAME 6.1.37-1-lts #1 SMP PREEMPT_DYNAMIC Sat, 01 Jul 2023 17:31:09 +0000 x86_64 GNU/Linux
~ » pacman -Q plasma-desktop
plasma-desktop 5.27.6-1