Hi.
SageMath runs on macOS 10.13 and newer.
macOS 10.13, 10.14 and 10.15 are NOT "too old" for SageMath.
There was indeed a problem with SageMath-10.6_x86_64.dmg, which has been promptly corrected by Marc Culler in the following version.
Please get
SageMath-10.7_x86_64.dmg
from
Everything works, including JupyterLab notebooks.
Beware: You are advised to use Firefox (version 115 ESR) instead of Safari or Chrome.
HTH,
Guillermo