The current build [linuxcnc-2.8.0-pi4.img] has an error with the 8GB version of the raspberry pi 4 where the USB does not initialise and leaves the machine booted but missing interface via mause / keyboard etc.
I am impressed that you found the right place to submit the issue report.
I tried a number of fixes, and published an image limited to 3GB. Very much a stopgap.
The current build [linuxcnc-2.8.0-pi4.img] has an error with the 8GB version of the raspberry pi 4 where the USB does not initialise and leaves the machine booted but missing interface via mause / keyboard etc.
xhci_hcd 0000:01:00.0: can't setup: -110 xhci_hcd 0000:01:00.0: init 0000:01:00.0 fail, -110
Various people have documented here; [https://forum.linuxcnc.org/9-installing-linuxcnc/40466-linuxcnc-2-8-0-pi4-img-no-usb-on-raspberry-pi-8gb]