As the first tranche of the (up to) $100k worth of Cash Flow Boost payments start coming in this week, the FAQ is where do you code the amount received into your accounts?
As the payment is tax-free (yay!) and also has no GST attached to it, I suggest that you don't merely put in your default income account of Sales or Consulting fees nor the Miscellaneous income account but rather set-up a new income account called "Government Grant".
This new account will hopefully stop you from inadvertently remitting GST back to the Australian Taxation Office in your next BAS nor pay tax on it at year end (like I know some businesses will do!)