Retrieving File Type using PnP Core SDK

Question

With PnP PowerShell, I am able to get the value of "File_x0020_Type" like this:

$item = Get-PnPFile -Url $file.ServerRelativeUrl -AsListItem
Write-Host $item.FieldValues["File_x0020_Type"]

However, I am not able to find the equivelant code from PnP Core SDK. When I tried to run this code

var item = await f.ListItemAllFields.GetAsync();
Console.WriteLine(item["File_x0020_Type"]);

where f is an IFile already loaded, it throws error:

PnP.Core.ClientException: 'Property File_x0020_Type does not exist in this entity'

If I run this code

var item = await f.ListItemAllFields.GetAsync();
Console.WriteLine(item.Values["File_x0020_Type"]);

then I get error:

System.Collections.Generic.KeyNotFoundException: 'The given key 'File_x0020_Type**'.

I don't want to get the File Type from the file extension name because I've seen that it is possible for "File_x0020_Type" to be different from the file extension name, which was causing some issues for our client.

And because to query a large library using PowerShell is quite slow, I am trying to create a .NET6 console app utilizing PnP Core SDK instead.

Any help is very much appreciated.