I recently had to upgrade the OS on my moms Air and it was a pain in the butt because she ignored updates for so long that all the SSL authority certs expired and the internet didn’t work. Plus Apple’s upgrade software was no longer supported by the servers – server wanted 2fa, moms laptop was too old to know what that is.
After a few manual hops, she is now smoothly running the latest and greatest MacOS on a 9+ year old laptop. Everything works fine.