Manjaro runs great on my MBP 2012. Or you can turn your MacBook Air into a "hackintosh" and install the latest macos on it using OpenCore Legacy Patcher [1]. Just be aware that recent version of macos relies heavily on hardware acceleration (video playback, cryptography, etc) and will fallback to CPU on older unsupported hardware, which is slow and deplete your battery fast.

[1] https://dortania.github.io/OpenCore-Legacy-Patcher/