My guess is that a 2015 Macbook Air is probably not going to run a MacOS version that is still supported by Apple. That would be yet another reason to simply install Linux. Before you do so you can go for https://rescuezilla.com/ and do disk cloning to an image that you save to some storage like a USB disk. If you do the same after your installing and tweaked Linux installation, you can have the best of both worlds whenever you need it.