Battery health in Big Sur?

Not on missing my MacBook Pro running Big Sur.

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.

You can go to Apple menu > About this Mac > System Report > Power - Battery Information - Health Information