Important Update: it is documented behavior, but there is a workaround that can be used posted at dotnet/runtime#61096.
The issue has been reproduced by running the app in a raspberry pi with raspbian. The app was built in a x64 windows environment, by using dotnet publish, such like:
dotnet publish .\SpanCastFailure\ -r linux-arm --self-contained -f net5.0
The issue was reproduced regardless of using --self-contained or --no-self-contained. The issue was also reproduced by using a recent daily build of net6.0.
When running on windows it prints this as expected 000000. While running on linux-arm it throws: System.DataMisalignedException: A datatype misalignment was detected in a load or store instruction.