Upgrade mother board

What is your model MacBook Air? Identify your MacBook Air model - Apple Support

Devices that are too old cannot run the latest version OS.

macOS Ventura is compatible with these computers - Apple Support. For MacBook Air, that is 2018 model or later. Earlier models are not suitable for this latest OS.

Somebody said I could change the motherboard.

Almost never for laptops. Almost never for Macs. The original model motherboard is usually the only one that is suitable for the rest of the laptop. It is all quite custom designed per model.

Upgrading the motherboard is more for build-your-own-desktop-PC users, with modular components and relatively expensive components in expansion slots.

You need to buy a new Mac. Nothing in a MacBook Air can be upgraded.

Which macbook Air do you have?

my wife has a 2019 & the logic/motherboard died during Ventura upgrade.

This happened to me as well. Trying to get help but all the standard suggestions don't apply.