Fred:
> On 4/23/22 02:34, karl@??? wrote:
...
> > So, make sure you are running in a virtual console and logged in as
> > root, then run the gpm -b etc. thing and move the mouse around.
> >
> > To make the mouse to work in X11, please test the mouse with gpm in
> > a console first to assert basic functionality, and then come back.

Did you do the test above ?

As long the serial port isn't opened by anything,
you can let X11 and openbox be running.

If so, press Ctl-Alt-F2 buttons simultaineusly to get to a console.
There log in as root
and then try one of
gpm -b 1200 -m /dev/ttyUSB0 -t msc
gpm -b 1200 -m /dev/ttyUSB0 -t sun
gpm -b 1200 -m /dev/ttyUSB0 -t mman
and move the mouse to test.

> A previous post mentioned xorg.conf which doesn't appear to exist in
> Devuan Beowulf (AMD64).
> So, where do I go from here?

You can either
A, do a xorg configuration with the mouse driver
man xorg.conf is your friend.

B, try inputattach to make the mouse appear as a /dev/input/* device
and be automatically included by X11, I haven't tested this. See

https://wiki.archlinux.org/title/Serial_input_device_to_kernel_input
https://sourceforge.net/projects/linuxconsole/files/
https://help.ubuntu.com/community/SerialMouseHowto
https://wiki.alpinelinux.org/wiki/Serial_Mouse

Regards,
/Karl Hammar