Marlin 2.0.x connection issues a possible fix suggestion

downloaded the trial version of LB 9.20 a few days ago. Using a Anycubic I3 Mega S 3D printer outfitted with a 20W laser controlled thru the FAN0 port. The anycubic is a trigolilla 3 board running Marlin firmware. Connection is USB. When I connect LB to my printer - it can recognize it as a GRBL-M3 (1.1e or earlier). However I can get any movement of the laser or table - - I do see string of LB sending G0 commands to the printer. Baudrate confirmed @ 250,000.
Any suggest