How to query the actual value in Entity Framework core when using a Value Converter?

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We have a fairly simple situation where an EF Core entity contains a value object that we map to a string:

```
builder.Property(_ => _.Nummer)
.HasConversion(i => i.ToString(), i => ZijdeNummer.FromString(i))
.IsRequired().HasMaxLength(9);
```

This works fine for retrieval and storage, but for filtering we're looking for a way to filter rows by substring. If it'd be a normal `string` column you can simply do something like this:

```
dbSet.TheTable.Where(t => t.Nummer.Contains("some text")).ToList()
```

Obviously the custom `ZijdeNummer` doesn't contain a recognized `.Contains()` method. I've tried using `.ToString().Contains()` but alas, this also doesn't work.

Finally, I've also tried accessing the column as if it were a shadow-property:

```
dbSet.TheTable.Where(t => EF.Property(t, "Nummer").Contains("some text"))
```

But it won't be fooled as it still knows that `EF.Property(t, "Nummer")` is not actually a string :(

Lastly I've dabbled in using a combination of `HasDbFunction()` with `HasTranslation()` but I couldn't get this to work, and also seems like a very difficult way to perform something that in its core seems so simple.

Is there a way to make EF-Core just query the raw column type? Any help would be greatly appreciated.