As far as I can tell, as long as you pay for a unity asset and you don't just resell it by itself, you can use it in whatever way you want.

For example, if there's a nifty networking library for Unity and I adapted to use it somewhere else, as long as I don't resell the library, I should be fine. Practically I can't imagine an asset store author suing you for using the asset in a non-unity project.

I do vastly prefer a single language engine like Stride, versus Godot which supports visual scripting, GD script, and C#.