Not sure if this is exclusive to the device (Ortur Laser Master 2) or to the plugin (Better Grbl Support) but curious if anybody else has seen this issue.
I can only connect to the LM2 if "Auto" is selected in both the port and the Baud Rate. If I loose connection (after OctoPrint selects the correct options) I have to set them both back to "Auto" before the connection will be successful.