Hmm, that’s strange. Can’t think of much else that could prevent that system from displaying anything.
Since you mentioned safe graphics work, can you try enabling the automatic login for your user in GNOME/KDE so the login screen gets skipped?
If that doesn’t work: After booting in normal mode, wait a little bit until it should be at the login screen and then hit Ctrl + Alt + F6 a few times. Does a terminal appear on your screen?
If you are willing to put in some work, Valetudo is fantastic: https://valetudo.cloud/
My two robot vacuums have been working for 5 years with no intervention other than emptying the bin every 2 weeks and dusting off the sensors when it complains.
Same as above, if you are willing to put in some work, Home Assistant includes a voice assistant and they ship devices now with everything preinstalled so you can plug in and go: https://www.home-assistant.io/green/