[phony-account]

> Macbook Airs that are only 3-5 years old

MacBook Airs from 2020 support Sequoia - so just the very upper limit of your range is relevant.

[wannacboatmovie]

Absolutely not. Apple was still selling non-Retina Intel MacBook Airs until 2019. Those are now completely unsupported with no security updates having topped out at Monterrey. 5 years of updates on a new laptop is borderline criminal.