Sets the suffix to be displayed after the value. You can use this for units of measurement.
gauge.setSuffix(suffix);
String
#include <Arduino_MKRIoTCarrier.h>
#include <Arduino_OplaUI.h>
MKRIoTCarrier carrier;
OplaGauge1 gauge1;
void setup() {
carrier.begin();
gauge1.begin(carrier.display);
gauge1.setSuffix(" km/h");
}