Calibration of Dexcom g6, (which I still have but also know will become obsolete as Dexcom stopped production)

How do I know if I’m accurately calibrating via glucometer reading results if I don’t use glucometer control solution? (I only recently learned there’s such a thing as control solution.) Is there any brand of glucometer, (old-fashioned finger-prick that provides BG reading via blood on test strip). that DOESN’T require control solution?? If so, what is it? I’m asking because earlier I used my True Metrix glucometer to try to verify my Dexcom g6 reading of 52, but my glucometer result was 190. I didn’t bother to calibrate the Dexcom at that time because of the significant difference. Shortly thereafter, my receiver showed “No Alerts/Alarms”, (under which says “Sensor Error Help”), and STILL says that (an hour later, at least).