When I look at the list of non-supported Macs, it is concerning when purchasing used equipment. As an example, a 2015 MBP with a last manufacture date of 2018 may have several years more OS support than the prior year model with a last manufacture date of 2015!!! With the latest OS update comes updated security protocols. Many sites are not accessible or will not properly run if current security is not updated. Does anyone have accurate information as to how Apple decides to not support the latest OS on a Mac model? I have read that it’s based on 7 years from the last date of manufacture, and also other reports that it is based on 7 years from the first date of manufacture! I’m not sure which is true and would like to generally know when purchasing used equipment. Does anyone have definitive information?