During smoke test of CuraLE 3.6.4 on Debian Stretch system, kept getting "failed to determine installed firmware version" error when connecting to the following printer/toolhead configurations:
LulzBot Mini with LCD Attachement/Single Extruder v2.1 Tool Head
Taz6/LulzBot TAZ 6 MOARstruder Tool Head
However this did NOT happen when we connected it to our Mini with LulzBot Mini Macro Extruder (HS 0.8mm)
In all cases, user is still able to connect to printer, send commands, flash FW and start print. However the Mini(LCD) test ran into a another issue after print command was sent from CuraLE and then attempted to abort a print. When user hit abort, there was no response from the printer as if the printer had become disconnected after the print started. Status on CuraLE had changed to reflect print had stopped but LCD was still showing that the print was underway. Had to click on disconnect and reconnect in CuraLE in order to reconnect to printer and that caused a "printer halted HEATING FAILED" on LCD.
Here is the log to the Taz6 test: