Just posting that the LLBLGen entities and ORM dll for .netstandard 2.0 target runs under mono in web assembly using the compact25 serializer, which is great. Just needed this linker config for the reflection:
<assembly fullname="SD.LLBLGen.Pro.ORMSupportClasses">
<type fullname="SD.LLBLGen.Pro.ORMSupportClasses.EntityBase2"/>
</assembly>