The missing cursor was caused by the Kensington trackball not yet
being registered due to a USB enumeration timeout on a sibling hub
port (usb 3-3.4.4, error -110). The cursor appeared once the timeout
completed and the mouse registered. MUTTER_DEBUG_DISABLE_HW_CURSORS
was not needed and has been removed.

The real fix is /etc/modprobe.d/usb-timeout.conf setting
usbcore initial_descriptor_timeout=2000 to reduce the per-attempt
timeout from 5s to 2s.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>