Azurerm_linux_function_app - dotnet-isolated 5.0

We have been using/creating azure linux function apps for some dotnet-isolated functions prior to the new azurerm_linux_function_app resource . However, this new resource does not allow the creation of setting the linuxFxVersion manually as it is determined automatically but we are unable to set the dotnet version to 5.0 as well as setting use_dotnet_isolated_runtime= true.
Are we just missing a step or config or is this just not working at this time. Thanks!