Hello
It seems that the issue you're encountering with SQL Server Linked Servers after upgrading to Windows 11 is related to authentication and the Kerberos protocol.
Linked Server Account Mapping Issue: You might encounter these error messages because of a linked server account mapping issue. You can correct this error by forcing TCP/IP or granting the appropriate permissions. In the Linked Server security dialog box, select "Be made with this security context" for a successful SQL Server login. When you select "Be made without using a security context" option, you will see the error message: "Login Failed for user NT AUTHORITY\ANONYMOUS LOGON" .
Windows Defender Credential Guard: Disabling Windows Defender Credential Guard has been reported to resolve similar issues. You can manage Credential Guard settings through Group Policy .
Group Policy Settings: Go to Group Policy and select LDAP for signing none in security settings, then try to go around RPC to authenticate everything and finally check Kerberos armoring in Group Policy with KDC. Try disabling Group Policy computer configuration and user configuration and restart the computer to try again .