I know a little more now:
I straced xfce4-session from the xinitrc. In the output, there was a suspicious call to xkbcomp. So I removed the executable bit from /usr/bin/xkbcomp, and voilà, my .Xmodmap works. I'll try reverting to a previous version of xkb-data and xkb-utils next.
I know a little more now:
I straced xfce4-session from the xinitrc. In the output, there was a suspicious call to xkbcomp. So I removed the executable bit from /usr/bin/xkbcomp, and voilà, my .Xmodmap works. I'll try reverting to a previous version of xkb-data and xkb-utils next.