In March 2019 Garmin announced that the Garmin G3X Touch system had received FAA approval in accordance with FAA STC SA01899WI that allows the non-TSO EFIS system to be installed in certified aircraft. Now more than one year later Garmin announced that the FAA STC finally has been validated by the EASA. The STC installation manual is about 500 pages and the basic installation manual for non certified aircraft is close to 1000 pages suggesting that the installation of a G3X will require careful planning and that the installation cost will be significant as it will affect the whole instrument panel and most likely require a complete rework of all avionics. For aircraft not limited to VFR a Garmin G5 EFIS must be installed as a backup standby instrument adjacent to the G3X EFIS display.
For more information refer to: https://buy.garmin.com/en-US/US/p/682215