Comment by blokey

It's not the macOS 26, its the option is not available on Apple Silicon machines. I think it is always enabled.

https://support.apple.com/en-mn/guide/mac-help/mh40774/15.0/...

Turn Power Nap on or off for a Mac desktop computer On your Mac, choose Apple menu > System Settings, then click Energy in the sidebar. (You may need to scroll down.) Turn on Enable Power Nap. Note: This option is only available on Intel-based Mac computers.

You can see (and change) the settings via Terminal, 'pmset -g' will show the current options.