Nerys NymeiA C EnderMy take is that because we chose to engage in a hostile relationship with them, they will kill is on sight, preventing anyone from discovery of their origin. The fact that they can also interdict you during a hyperspace jump suggest that they may have another understanding of reality than us, or even come from another reality. There's also the fact that we effectively only jump from one system to the next: we never travel the void between. Where are we hyperdicted? In the void between. The void is massively larger than any system.
There's plenty possibilities why mankind know nothing of them.
It has been suggested that they "live in the hyperspace" or that "they are not of this galaxy", and this could be a valid explanation of why we have not yet discovered their main planet.
But when they attack our ships, they are here, and when we destroy theirs, they leave a lot of wreckages. Not a single body has been recovered? Not even a finger? A Thargoid battlefield should be the heaven of each xenobiologist in the galaxy, yet nothing is known about them. I find it a bit irrealistic.
The moral of the story? FDev, fleet carriers are fine, but now please give us also a bit of lore!
Thargoid ships have been studied and researched. In fact, our FSD is based on thargoid technology, reducing the duration of a hyperspace jump from hours to seconds.
This is from the wiki on Thargoids. Lots of information there on some of the topics we've discussed. They've definitely been researched, although no "thargoid" have been found. Although, I see this as two possible explanations; their ships are drones and need no pilots, or humanity have missunderstood their existence, and the ships themselves are living. It's known/hypothised that they have a hive-like structure. It's not a far stretch to think that they have a physical presence significantly different from ours, either multiple "digital" or as a singular entity. Not that different from the antagonists where my namesake come from.