SAM 2020.11.29 requires OS X 10.9 or later.
NREL does not have an Apple code signing certificate for SAM. If you see a message about verifying SAM that prevents you from starting SAM:
For some older versions of OS X, a security feature called Gatekeeper may prevent you from starting SAM. For more on bypassing Gatekeeper, see this CNET article.
If SAM does not display correctly in macOS Dark Mode, close SAM, switch macOS to Light Mode, and then restart SAM.