The reason for the unknown commands and most built in buttons not working is the aforementioned confusion between GRBL and Marlin. Setting the machine up as GRBL makes Lightburn default to GRBL commands, which Marlin doesn’t understand. So for a lot of things, like movement, you either have to hand-type the commands in the console, or set up your own macros.
Using the “Snapmaker” device in Lightburn makes engraving super slow as it uses the old stop/go method for each dot vs pulsing the laser. (I could be wrong about this and they’ve recently updated the snapmaker profile to have inline, maybe one of the LB team can chime in).