Greetings. Name here is Stephen, I live in Northern Lower Michigan.
I have a Garmin GPSMAP 86sci, similiar to the 66i. I wanted the ONX Hunt Chip product to use to find plat boundary lines--adjacent to state land--in the Northern Lower Peninsula of Michigan, where I live.
I spoke with a Garmin rep today (11/25/2020)--who said he's been with Garmin for some time--about the ONX Hunt Chip, and was told that, at one point, ONX was considering Garmin as a Partner, so Garmin asked ONX for royalties, which ONX wouldn't (or couldn't) deliver on, so Garmin coded out the ability of the newer In-Reach products and the newer Montanas, to decode and read the ONX Hunt Chip maps, The older units (64 series, Oregon, etc.) do apparently work, as indicated on ONX's web site.
So, perhaps, we can petition ONX to work out a royalty agreement with Garmin and get these wonderful units, with a worldwide satellite communication safety net, to accept the ONX chips.
Just thought I'd pass this information along.
Warm Regards,
--Stephen
(Note: The above is, of course, Garmin's information, and not that of ONX. I called ONX, and they said they had the ability to code for either/or, but not both, which, to me--as a GIS/Cartography Hobbyist--doesn't make a lot of sense, unless it has to do with ONX's ability to license their maps for the newer units; availability of working money for licensing, in other words.)