Ok. Here is how I ended up being able to run turbo tax on my older mac also running High Sierra. This Mac has 16GB of RAM.
1. Since I already had Parallels loaded on the Mac to run Windows for another project, I upgraded Windows (within Parallels) from 7 to 10 for $139.
2. Installed TurboTax on Windows 10. $49
3. Upgraded Parallels and there was a Windows 10 update as well. $0.
4. Started TurboTax within Windows 10 which was within Parallels.
5. Waited, and waited until everything settled down and did the usual TurboTax update. This took a huge amount of time to initially load and run because it was installed within a virtual machine.
6. Kept Windows 10 running in the background via Parallels on the Mac so it did not have to relaunch stuff all over again.
7. Launching TurboTax now seems to be happier when opening and is reasonably responsive.
8. Total cost this year to file taxes on a local copy of TurboTax $188. Far less than having to buy a new MAC to use TurboTax.
Might help someone or not; but it works and since Windows 10 appears to be likely supported for the near future, it might be a workable solution to try.
