Does any other gcode sender work on the same system? (If you are using Windows, it’s famously persnickety about USB drivers.)
Vis-vis updated firmware, the latest I know of here is from your earlier thread:
Here is someone with unrelated problems on the same controller board running another build not with the Hobby-Fab spindle non-linear profile parameters:
https://forum.lightburnsoftware.com/t/lasers-and-motors-stop-within-10-seconds-of-starting-engraving-help/7943
Lightburn intends to support grbl 1.1f, the version of the firmware from Hobby-Fab, with the GRBL device type. It looks like the Hobby-Fab version is branched off 5967839ab38f8e984a384db1f64e781cffb9e739 Looking at the diff, I don’t see any pin mapping changes, so the default CPU_MAP_ATMEGA328P looks lke it applies. This means that I think you could build upstream latest onto the board and restore your $$ dump if you don’t want the spindle profiles from Hobby-Fab.