builder.UseNpgsql(connectionString, p => p.UseJSON());
[Column(name: "attr", TypeName = "jsonb")]
public virtual JObject AttrObject { get; set; }
var data = query.Where(p=> (string)m.AttrObject["LowerFreq"] == "Test").ToList();
SELECT attr as 'Attr' Where attr->'LowerFreq' = 'Test'
Npgsql.EntityFrameworkCore.PostgreSQL >= 2.2.4