The official v5.7 release of ServiceStack with support for .NET Core 3 that a lot of you have been waiting for is now on NuGet. It also includes Async support for Server Events which should now be preferred when running on .NET Core 3 to avoid sync Response writes.
Please see the full Release Notes for the finer details:
Mobile OS’s aren’t a supported platform, I’ve heard of OrmLite.Sqlite being used in Android but it’s unlikely to work in iOS due to its JIT restrictions.