When sharing a map location from either Google or Apple Maps, you could previously share to Garmin Connect and use that to route to that location. This has gone missing in iOS26.
This looks to be an iOS 26 specific issue as others have reported the same throughout the iOS26 Beta. Those enrolled in the public beta are now receiving the final release version, so this bug will be present on release day unless there's a Garmin Connect update.
It's still possible to share a GPX file to the Connect App, however, so it's not all share cards the Connect is missing from.
I share this to raise awareness rather than looking for a fix, this will almost certainly be dependent on an update from Gamin. All other apps I use this functionality with are working fine - Wahoo, MyBMW among others, so I don't think this is an iOS bug.