I have Cura "Start G-code" with delay
M140 S{material_bed_temperature} ;Start heating bed
M105
M190 S{material_bed_temperature} ;Wait for bed to reach temp before proceeding
G21 ;metric values
G90 ;absolute positioning
M107 ;start with the fan off
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
G1 Z15.0 F{speed_travel} ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
G1 F{speed_travel}
G4 S300 ;wait 5 minutes
M104 S{material_print_temperature} ;Start heating extruder
M105
M109 S{material_print_temperature} ;Wait for extruder to reach temp before proceeding
where G4 S300 used to make 5 minutes delay to let the surface of glass to heat up to required temperature (600W 220V silicone heater, aluminum layer plus glass) because when M190 receives required temperature from thermistor surface temperature 5-10 degrees lower.
So when printing starts I have delay, firmware ignores it as delay and shows me astronomical numbers of time left expected. I have Duet2CombinedFirmware 2.05 downloaded from RepRap Duet configuration page.