No battery health in MacBook Air 2017?

Apple menu > About This Mac > System Report > Power > Battery Information - Health Information.

The top screenshot is how it should look with Big Sur 11.2.1 with the exception that the Battery Health button is missing. Two possible reasons for that from https://support.apple.com/en-us/HT211094?cid=mc-ols-energy_saver-article_ht211094-macos_ui-04022020

You may have a Mac that doesn't have Thunderbolt 3 ports. See:

Battery health management is on by default when you buy a new Mac notebook with macOS 10.15.5 or later, or after you upgrade to macOS 10.15.5 or later on a Mac notebook with Thunderbolt 3 ports.

or you may have a new Mac with the M1 chip instead of Intel:

This article applies only to Mac computers with an Intel processor.