Dependent ILR Application but Not Valid Passport

Hi all,
My friend (Indian) got ILR along with his wife and a daughter in January this year. His son (8 years old) who is still on Tier 1 Dependent visa (200K route- visa valid till May 10, 2020) has his Indian passport expired on January 20th, this year. He could not apply for extension of his passport as he had to travel abroad for business. He returned on March 3rd but Indian consulate in Birmingham is now closed. He contacted the embassy officials, but they are unable to give him any date on when can he get his passport apply and renewed. He is suggested that he need to call them back some times in couple of months to check if they are accepting passport renewal applications now? He is also told that he should be ready for "very long" delay in getting passport due to backlog of applications.

Can somebody please suggest me will he be consider over-stayer? Does he need to inform the Home Office in order to get any exemption or anything?

Can somebody please reply ......

All migrants must apply online to prevent becoming overstayers even if they do not have all the documents
They should then only book and appointment when they have all the documents. They should apply online before visa expiry and put an expiry date for the passport to satisfy the online form. Then provide a cover letter with the new passport during the appointment !