I have a 15-inch Retina MacBook Pro from somewhere between mid-2012 and mid-2015, currently running macOS Monterey 12.7.6, which appears to be the newest officially supported version. I mainly use it for web browsing and other light tasks. Using unofficial tools such as OpenCore Legacy Patcher, could I install macOS Sonoma or Sequoia, and which newer version would provide the best balance between features, security updates, and acceptable performance?
4 Answers
Before choosing a version, verify that the applications and browser you rely on still support it. The newest installable version is not necessarily the best experience: an officially supported Monterey installation will generally be less troublesome, while a patched Sonoma or Sequoia installation trades convenience and speed for newer security support.
If the Mac has 16 GB of RAM, Sequoia may run reasonably well for basic use and would provide a newer system with ongoing security updates. With 8 GB or less, Ventura or Monterey is likely to feel more comfortable. Either way, make a full backup first and expect that some updates may require reapplying the legacy patch.
OpenCore Legacy Patcher can let these Macs run versions as new as Sequoia, but that is an unofficial setup. Sequoia may feel noticeably slow, especially on older CPUs or machines with limited RAM. For light browsing it might be usable, but Monterey is likely to remain smoother and more reliable.
Unofficial upgrades are possible, but older Retina models can need workarounds for graphics drivers and other hardware features. Ventura is often a more practical performance ceiling on older machines, while Sonoma or Sequoia may require more troubleshooting. Check the specific Mac model, graphics chip, RAM, and the patcher's compatibility notes before upgrading.

Modern websites can be demanding even when the operating system itself seems usable, so browser performance may become the real limitation rather than macOS alone.