Can a server outside the Windows domain connect to a 2nd SQL instance via a linked server?

I have the infrastructure shown in the diagram below. Web Server 1 is outside the Windows Domain. Web Server 2 is inside the Windows Domain. SQL Server 1 and 2 are both inside the domain. There is a linked server connection from SQL Server 1 to SQL Server 2. Both SQL Servers only accept Windows Authentication, not SQL authentication. Both SQL Servers have a Kerberos SPN setup with unconstrained delegation. A domain user on Web Server 2 has a SQL login configured on both SQL Server 1 and SQL Server 2 and can query data on SQL Server 1 and on SQL Server 2 via the linked server. A local user on Web Server 1 has a local login of the same name and password configured on both SQL Server 1 and SQL Server 2 and can query data on SQL Server 1, but not on SQL Server 2 via the linked server. The following error is given in the SQL Server log: *Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'. Reason: Could not find a login matching the name provided.* The question: can Web Server 1, outside the Windows Domain, be made to successfully query data from SQL Server 2 via the Linked Server connection on SQL Server 1? If so, how?