Pilot on final approach to a non-towered airport reported an NMAC with another aircraft not communicating on CTAF.

Narrative

I was returning north along the coast of Jekyll Island. Winds were out of the south; so Jekyll was using Runway 18 and St Simons/KSSI was using Runway 22. I had been making and monitoring radio calls; never having left the vicinity. I also had the traffic screen active on our Garmin 750. I was descending from 2000 ft. in preparation for landing at Jekyll/09J. As I was turning west; I glanced out the right side window and saw another small aircraft climbing in very close proximity.I turned down and left; but the other aircraft was already behind me at that point. I doubt if he ever saw me due to his nose-high attitude. Key things I learned/reinforced. Eyes always actively scanning outside; don't get overly dependent on ADS-B. Don't assume others are making radio calls at all; making proper radio calls; or even on the right frequency. Lights on in the vicinity of an airport will help everyone. Be especially cautious when crossing in the vicinity of another airport; particularly with closely aligned runways. I probably should have been down lower at that point; where most of the traffic would have been flying level and everyone had a better chance to see and avoid.