How do I sync iPhone contacts to inReach Mini?

You cannot do so - and I’m not sure why you want to. You can use those contacts when sending a message via the app. most people have hundreds of contacts on the phone. Many of which they would never use with inReach.

OK, thanks.  I am an atypical cell phone user and only have few contacts in my phone.

I could not do it with my inreach explorer.  Really annoying.  My guess is Garmin and Apple see each other as competitors so they don't cooperate and we all suffer. 

Possible, but I don't think that's the reason. The Garmin inReach software ecosystem is pretty bad, IMHO. I don't know what it looked like in the Delorme days, but I suspect nothing much has changed since they became part of Garmin. There is very little integration with the rest of Garmin, and everything seems way too confusing. Just my opinion, of course, but as a long-time Garmin recreational device user (watches, cycling, etc.), I was unpleasantly surprised at how separate the inReach systems are from the other parts of Garmin I've been using. Even just for inReach, why do we have Explore *and* Earthmate? Why aren't they one? And why can't this stuff be integrated with Garmin Connect? Rant over. :-)

The issue here is the age of the various devices.

The true "legacy" devices - SE+ and Explorer+ - still operate entirely with DeLorme software (now Garmin-branded, but same functionality as the original DeLorme software). For example, the Earthmate mobile app. This also applies to the maps on the legacy devices which have them. They still use maps in the old DeLorme format. Data sync is via the Earthmate app or via wired sync using the desktop Sync program. F/W updates via wired sync. I doubt that this is going to change.

The Mini has one foot in each universe. It still uses the Earthmate app to sync. F/W updates via Garmin Express. I honestly do not remember if it also does data sync via the wired desktop Sync. Maps are not available.

Beginning with the 66i, inReach devices are full members of the Garmin handheld family. They use standard Garmin maps. They get f/w updates via Garmin Express. They sync data via the newer Explore mobile app. (OK, I know the Explore app is not part of the standard Garmin handheld universe. And it's a buggy acquired taste. But more and more Garmin handhelds and wearables are going there.)

I understand, but it's still disappointing that Garmin won't invest in bringing these devices into the modern Garmin software universe. And consolidating the universe.