The Gigabyte GV-N105TOC-4GL is only 37mm tall, it is specified as Low Profile, and includes
Two 2 HDMI 2.0 ports
You could add an HDMI-VGA adapter for the VGA when needed, or perhaps you could use the motherboard video port of that Dell Optiplex 780 for VGA monitors in parallel with the add-in card; Gigabyte could ...
The XPS with a i7-10710U has more processing cores than the i7-8665U which could help it tackle multiple simultaneous programs or threads. Performance improvement in programs, which are not memory-bound will be lower. It could take advantage of faster memory access, but Dell chose slower memory for the XPS. Ouch!
The Latitude with a Core i7-8665U advantage ...
Check that the monitor power cable and HDMI cable are securely plugged in. If the issue still occurs the cable is probably bad, replace it and see if that works. If that doesn't fix it, either the HDMI port on the monitor is bad, or the HDMI port is bad in the GPU. The ports shouldn't have gone bad after a maximum of a month of usage though.
Question: Do your monitors have multiple inputs?
My Acers take HDMI, DVI & VGA. I have plugged my work laptop in on HDMI, personal laptop to DVI. A third antique computer connects to the VGA.
The main desktop (where Windows bar sits) is on left monitor, but MacBook Pro’s main display is the right monitor. Both laptops extend their desktops onto the ...