Upsert inserts empty values

[enriquinho-catalan]

With definition of

public enum MyEnum
{
    X = 0,
    Y = 1,
}

public class MyGroup
{

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public long MyId;

    public MyEnum en;
}

MyGroup is marked as having an int conversion in model builder launch context:

            entity.Property(e => e.en)
                .HasColumnName("column_name")
                .HasConversion<int>();

The following upsert command yields the following SQL:
INSERT INTO "my_table" AS "T" () VALUES () ON CONFLICT ("my_id") DO UPDATE SET "en" = $1
Columns and values are left empty, which I believe is a bug.

    var myGroup = new MyGroup
        {
            MyId = 1,
            en = MyEnum.X,
        };
    
    _dbContext.MyGroups.Upsert(myGroup).WhenMatched(group =>
        new MyGroup
        {
            en = myGroup.en,
        }).Run();

If I try using the 2 parameter WhenMatched method, I get a different error:

    _dbContext.MyGroups.Upsert(myGroup).WhenMatched((dbGroup, insGroup) =>
        new MyGroup
        {
            en = insGroup.en,
        }).Run();

I get the error
This type of expression is not currently supported: insGroup. Simplify the expression, or try a different one .See https://go.flexlabs.org/upsert.expressions for more details