Possible Workaround.

Note - Quickbooks employees, NO need to respond to this, please. This is just for fellow QB users who may find it useful.

Re "offline mode" - I am running QB Desktop Mac 2021 (V20.0.7 R8.1 / Build 908). I have Little Snitch (an outgoing network connection manager / blocker) set to deny QB any outgoing network connections. So my desktop's connected to the internet, but QB, effectively, is not.

When I start QB up, the "Log In" dialogue window pops up, but there's no content in it, and I have the option to hit "cancel" at bottom right, and continue to work on QB.

I'm not sure whether this is "offline mode", not sure how long it's going to last functionally, and (along with all of the rest of you) sure as heck I don't like this intrusion on our privacy and work efficiency by Intuit ... but it may be a useful workaround for some other Mac users out there.