NDP-18.5 proposes to add a definition of “government institution”, and it's amending section 2 of the Library and Archives of Canada Act.
House of Commons Procedure and Practice states on page 654:
...an amendment is inadmissible if it amends a statute that is not before the committee or a section of a parent Act unless it is specifically being amended by a clause of the bill.
Since section 2 of the Library and Archives of Canada Act is not being amended by Bill C-2, it is inadmissible to propose such an amendment. Therefore, NDP-18.5 is inadmissible.