MacBook Air displaying 'support.apple.com/Mack/startup' and how do I fix it?

"Why is my MacBook Air I started displaying support.apple.com\Mack\startup how to fix this"

The Startup Disk is Corrupted.

This is the same error as when you see question mark on your Mac at start up:

So, a few things here:

Unplug All Peripherals. Then...

Run First Aid, then Mount the Drive, in Recovery Mode:

A. Go here: How to Repair a Mac Disk with Disk Utility - Apple Support. Boot into Recovery Mode (Intel or Silicon). Using Disk Utility, see if the Hard Drive is seen. If it is, then see if you need to click the “Mount’ button for it. Try rebooting once more. If of no success, then click unmount button, and then the mount button. Try rebooting once more.

B. Restore froma Backup:

Did you ever back up your Mac with Time Machine Backup prior to all of this? If so, restore from it.

C. Reinstall the macOS:

Go Here: Reinstall macOS - Apple Support.

Boot into Recovery Mode (Intel or Silicon).  Important: Prior to installing an update or performing a reinstallation, to prevent data loss, be sure to Back up your Mac with Time Machine.