Filing of return

Yes, it is mandatory to quote Aadhar Number or Aadhar application number to file personal income tax return, there is nothing to do with linking of Aadhar Number with PAN has been extended upto 31st March 2021

Yes its mandatory

Every thing that income tax dept thinks is for our good only.... there are no of advantages of linking adhar with pan .
1) you can e verify your return so that you need not send your physical copy of itr v to cpc banglore.
2) Any way income tax authorities get to know about your adhar number through the bank account you linked, tds forms your employer made , from lot of other sources.

So if it is possible just link your adhar to pan other wise just quote your adhar number in your return. why to take risk of not quoting adhar number.
any ways it's mandatory.