Auto login not available

SomanyQs wrote:

Why is my Auto login not available big Sur

If you have enabled encryption ( FileVault )then you do not have the option for Auto login.

You can check and decrypt from >System Preferences>Security & Privacy >FileVault

Encrypt Mac data with FileVault - Apple Support

Use FileVault to encrypt the startup disk on your Mac - Apple ...

Set your Mac to automatically log in during startup

What do you mean it's not available? Did you check System Preferences > Users & Groups > Login Options?