Creating MemoryMappedFile fails with PlatformNotSupportedException

I am having the same problem as issue #21863 but the solution given by stephentoub on May 22, 2017 does not work.

I am trying to create a shared memory using dotnet 5.0.2 on CentOS 8.
My instruction of
mFileMap = MemoryMappedFile.CreateOrOpen(this.Name, OVERHEAD_SIZE + Capacity);
fails with a: System.PlatformNotSupportedException: Named maps are not supported.
Replacing the name with a null gives: System.ArgumentNullException: Map name cannot be null. (Parameter ‘mapName’)

How do I fix this?