And now I"ve booted up this original installation mentioned in the quote above and can confirm now: this setxkbmap command "forgetfulness" does not happen here. Even though the USB keyboard detachment/reattachment does happen time to time:... What surprises me is I have seen such messages before. But it never caused the problem described in this discussion.
... I NEVER had it on my other 12* installation on the same machine but which was incrementally updated by freebsd-update.
Though it happens, the X session retains my ability to switch between keyboard layouts.
ugen1.3: <SIGMACHIP USB Keyboard> at usbus1 (disconnected) ukbd0: at uhub3, port 1, addr 3 (disconnected) ukbd0: detached uhid0: at uhub3, port 1, addr 3 (disconnected) uhid0: detached ugen1.3: <SIGMACHIP USB Keyboard> at usbus1 ukbd0 on uhub3 ukbd0: <SIGMACHIP USB Keyboard, class 0/0, rev 1.10/3.30, addr 3> on usbus1 kbd2 at ukbd0 uhid0 on uhub3 uhid0: <SIGMACHIP USB Keyboard, class 0/0, rev 1.10/3.30, addr 3> on usbus1
uname -routput for this installation is 12.2-RELEASE-p1. Same as for the other one where the original problem happens.