Thargoids ships are definitely made of organic and biological materials. The only manufactured elements are the ones that we can collect after destroying them.
My theory is that the Thargoid Ships are bodies.
There's no Thargoid inside, they control the body with an advanced telepresence, like in the Avatar movie.
When we destroy a ship the body dies but not the Thargoid that is controlling it. They clearly suffer incredible pain because we can hear them screaming but then they wake up in their control room in their mother ship (and then they maybe have to pay the body re-buy
).
So the bad news is that up to now we still haven't killed any Thargoids, we are just destroying their advanced avatar and that we will never be able to control any thargoid ship in the game.
This theory would also confirm the presence of hearts in the Interceptors. I came to this conclusion by looking carefully at the interiors of a scout that I destroyed yesterday that from the inside really looks like a body and not like a vehicle:
My theory is that the Thargoid Ships are bodies.
There's no Thargoid inside, they control the body with an advanced telepresence, like in the Avatar movie.
When we destroy a ship the body dies but not the Thargoid that is controlling it. They clearly suffer incredible pain because we can hear them screaming but then they wake up in their control room in their mother ship (and then they maybe have to pay the body re-buy

So the bad news is that up to now we still haven't killed any Thargoids, we are just destroying their advanced avatar and that we will never be able to control any thargoid ship in the game.
This theory would also confirm the presence of hearts in the Interceptors. I came to this conclusion by looking carefully at the interiors of a scout that I destroyed yesterday that from the inside really looks like a body and not like a vehicle: