Yea, some kind of converter for unity assets would be cool. But 3d assets should already work... And with other things from the Unity asset store you could run into licensing issue. But I don't know the details about that, might even vary from asset to asset.

Stride has pretty good written docs, for an open-source project. And there are quite some video tutorials on the docs page too. And there is also: https://doc.stride3d.net/4.0/en/manual/stride-for-unity-deve...