If I had an active subscription with Quixel megascans and their library, can I use their textures for my buildings for my upcoming asset store release? I am planning on launching this environment pack with buildings and other various prefabs along with this demo scene (more changes planned).
If not, where can I get textures to use for my asset?
This isn’t a legal advice forum.
However, I am thinking this is pretty clearly a NO. The things that you can include in YOUR asset for sale is pretty limited. If you made something with another asset tool, or you bought another art asset through a subscription, you cannot pass on THEIR rights to someone else who buys YOUR asset.
There is a very limited list of things you can use from the Asset Store, to include in YOUR assets you submit for sale, and only for demonstration purposes to show buyers how to use YOUR asset, not to pad out the asset’s content in your buyer’s game. https://assetstore.unity.com/lists/free-to-use-assets-for-publisher-demos-243675