As you have probably read, it is necessary to own Skyrim SE in order to play Enderal SE.
This has to do with Bethesda's licence rights to their engines.
Enderal (both the classic and the SE version) are treated like mods by Steam (they are total conversions...).
It is known that you can still download Enderal SE even if you don't own Skyrim SE on Steam. However, this is a technical matter on the part of Steam over which we have no influence. Unfortunately, as in your case, when you try to install the game you get the message "no licence".
Ownership of Skyrim VR is not intended by Bethesda as a prerequisite. So legally there is nothing you can do.
If you want to play Enderal SE, you have to buy a legal version of Skyrim SE (this also applies to the GOG version).