The issue

When connecting to a standalone computer with a PowerShell PSSession you get the following error:

WinRM cannot process the request.
The following error with errorcode 0x80090311 occurred while using Kerberos authentication:
We can't sign you in with this credential because your domain isn't available.
Make sure your device is connected to your organization's network and try again.

The explanation

PowerShell tries to connect with Kerberos, but Kerberos is only available for domain members.
At the same time, you have disabled all other authentication methods, either on the client computer or on the target computer.

How to solve your problem

1. Check available authentication methods on the client computer

   Get-ChildItem -Path WSMan:\localhost\Client\Auth
   

2. Check available authentication methods on the target computer

   Get-ChildItem -Path WSMan:\localhost\Service\Auth
   

3. Ensure you have a common authentication method
4. Specify this method in the authentication parameter of the command line

   Enter-PSSession -ComputerName MyComputer -Authentication Credssp -Credential $Cred