Have i to turn off or put in airplane mode(if any) Inreach Mini 2 during Flight?

You would do best to ask the airline directly. Unfortunately, the airline is unlike to understand the nature of the device...

You an also try opening a support ticket to see if Garmin has an opinion.

My assumption always was that anything that broadcasts on any frequency is regarded with suspicion by the airline industry and generally banned during flight unless specifically cleared. Bluetooth devices have been cleared for some time and now WiFi is allowed and even offered, but I don't think satellite communicators are going to make the list anytime soon. And since Mini (both versions) will always try to communicate with satellites when it's on, it's best left off on a plane.

Of course, it's not going to bring down the plane if you forget. But to be fair, I also don't think it's going to work very well inside an airliner. My experience with GPS on a plane is that it can get a fix if you put it next to a window for a while. If you have an aisle seat, forget it. And Iridium satellites will most likely fare worse than GPS. The hull tends to make a pretty good job of blocking signals/line of sight.