They would work but I'm not sure it's worth it. The 11" Air had a pretty terrible screen, and the models with 8GB of RAM are more expensive than I think they are worth. Plus Macbooks of this era are going to need a battery replacement, so your going to have to invest $70-100 on top of the price of buying the Macbook. You're likely going to be $200-300 invested into a 10 year old macbook.

Also keep in mind the 11" MacBook air wasn't that small. The Macbook neo with a 13" screen has almost the same dimensions.

For $300-400 you can buy a decent brand new chromebook, and running linux is officially supported on them. https://support.google.com/chromebook/answer/9145439?hl=en

The chuwi minibook is also an option, but I don't know how well linux is supported.