Hi, I'm a bit in the same situation and needed to seek extension for my initial entry date, which is the 12th Sep 2020. I submitted my request for an extension of the IED via this link (https://immi.homeaffairs.gov.au//help-support/departmental-forms/online-forms/australian-immigration-enquiry-form), and the answer I received (quoted below) is not very re-assuring. I found the info you shared very helpful, and your case has given me some hope. How did you submit your application for the extension of the "must no arrive after" date? Is there an email or an online form to write to? Thanks so much in advance for your advice.
Quoted answer from the Immigration Department following my request for IED extension due to covid-19:
"The first entry date condition is a legislative requirement and is attached to permanent and provisional visas granted offshore. It is not possible to waive the condition or vary the date, and visa holders who breach the first entry date condition may be subject to visa cancellation.
However, in the majority of cases, visa holders who are unable to make their first entry by the required date may be allowed to enter Australia at a later date, provided their visa is still valid and there is no other reason to consider cancellation of the visa."
