In order to use TurboTax for 2023, with Mac computers, the minimum system requirement is macOS Monterey 12 or later. You could choose either to upgrade your operating system if your device allows, go to a newer device, or use a Windows device.
The minimum system requirement to run the 2023 version of TurboTax is:
macOS Monterey 12 or later. See here for more information about the minimum system requirements for tax year 2023Mac.