So I'm not well known in the dotnet world especially with Core and NET project files. But since 3.2 I think the assemblies(the dlls) are placed in /.mono/assemblies/$(ApiConfiguration)/ where $(ApiConfiguration) is either a Release folder or a Debug folder. So once has to manually change the fsproj to reflect that.
I'm not sure how to fix this since I'm not familiar with the whole *proj file format. Any tips?