The latest version of Logic requires MacOS 13.5 or later and unfortunately you need a 2018 MacBook air or newer to install it. There is a workaround though that will allow him to download the latest version of Logic for his computer.
How to purchase older version of Logic for those without Ventura 13.5. You'll need to find someone with a mac that is running at least Ventura 13.5. Open the App Store. Log in with your user ID and purchase Logic. I'm not sure if it will try to download right away but if it does, I believe you can cancel the download.
Log out of the App Store for the newer computer.
Now go to your computer. I tried this on Mojave 10.14.6.
Open App Store. Login if you haven't. Select your account on the bottom left. Look for Logic Pro on your purchases. Do not click on Logic Pro itself. Click on the download symbol. It will bring up some message asking if you want to download the last compatible version. Click download and you should be good to go.