Has the optional Inreach GEOS SAR & Global MEDEVAC insurance been discontinued? And if so, are there plans to offer any supplemental insurance in the future?
I believe the memberships are still available, although perhaps not through Garmin (although Garmin now owns GEOS, so?). Calling this insurance is a misnomer. You must have purchase an appropriate membership plan from GEOS in order to get these benefits.
The additional GEOS services should be available to purchase through an active inReach account or when signing up for a new account. They were temporarily removed from the sign up process but are back. If you aren't seeing them, please try signing out of the Explore website, clear your web browser history and cache, then log back into explore.garmin.com.