There's been some changes to support php 7.4 which doesn't have money_format() and also some work towards locales. Most likely that's the cause. I'd open a lab ticket.
I'd guess this line needs to be changed to match the other changes that have happened:
I agree with what you said at the start of your paper, "QB looks at money from the perspective of the business (the primary concern is where the money is coming from, going to, profit and loss, health of business, successful/failing programs). The people who gave the money are only incidentally important. Civi (or any CRM) is primarily dealing with ...
It may be worth exploring the Civi extension already in place
QuickBooks Online provides different Tax APIs for US and non-US
countries. This extension has been developed and tested for QuickBooks
Online, Australia. With initial development ...