" I also know that there will be another 'final' tax return to be lodged when the estate is settled."
Why?
If your deceased father has no due or overdue tax returns and indicated his last tax return as his Final tax return then I question whether a non-lodgment advice form is necessary.
If you decide to complete one then you won't be able to complete it online.(a tax agent can). Paper form. (but you need his TFN).
Prior years only needed if he has overdue tax returns (on his ATO records) and didn't need to lodge those years.
If the estate has no income to declare (above $18,200) then a deceased estate tax return is generally not required. Guidelines below.
When and how to lodge returns for a deceased estate | Australian Taxation Office