A ship with the resource profile sensor will identify what type of gas a nebula cloud contains just like resources on planets and asteroids. Not sure why it wouldn't be identified if the explorer that you sent there was equipped with a resource scanner. Was the specific node (the little + that denotes a specific nebula cloud) that was showing up as unidentified visited by your explorers?
Yes, I had 5 explorer ships exploring the systems nearest my starting system, no problems with normal star systems, but when I sent them to explore the gas clouds, they traveled there, said they'd finished their mission, but when I selected the system it said unknown for resources. I tried telling them to explore the system again, but nothing happened.
I'm not running any major mods, ony a tiny set of tweaks I made myself, which only changes the speed values for hyperdrives and the damage value for missiles and missile bombers. I'll try again in a new game.
< Message edited by CariadocThorne -- 5/13/2020 11:44:40 AM >