For those still having issues with QBDM 2021, I've found that the key to hold down while opening is command, not shift. Doing this allowed me to get the side bar open and use all windows EXCEPT the home page, which will trigger the spinning wheel.
For those on QBDM 2019, QBDM 2021 is the LAST version of QBDM that is NOT a subscription model (1 time purchase only). QBDM 2021 has an end-of-life support set for May 2024, so they _have_ to fix the Sonoma issue, whereas 2019 has been end-of-life already.
