Это приводит к желаемому действию.
public RootsMagicContext(string databasePath)
{
var connectionString = $"Data Source={databasePath}";
this.connection = new SqliteConnection(connectionString);
this.connection.CreateCollation("RMNOCASE", (s1, s2) => string.Compare(s1, s2, StringComparison.OrdinalIgnoreCase));
}
protected override void OnConfiguring(DbContextOptionsBuilder options)
{
options.UseSqlite(this.connection);
}