LGPL is specific to the library. A proprietary application can ship with an LGPL library, as long as the library hasn't shipped with proprietary modifications.
But Unity can’t do that because it transpiles code on build… simply linking using LD wouldn’t make you have to adopt. Any modifications would, and would have to be published in source code form.
unity only does transpiling for C# to native code if you enable it in your project. it cannot transpile the (presumably) linked native library so this shouldnt be an issue here
