Hi Parcan64,
You can still install QuickBooks Desktop 2021 using the Ventura Mac OS. As long as the OS has the minimum Mac OS X v10.15.
You can check this reference for the detailed information on the compatibility: System requirements for QuickBooks Desktop for Mac 2021.
You can always visit our Help Articles page for more resources in managing your QuickBooks Desktop.
I'll be around whenever you have concerns with QuickBooks.
