How to copy list items with people and group columns between site collections using CSOM

spsp.cs

using System; 
using System.Collections.Generic; 
using System.Net; 
using System.Security.Principal; 
using System.Security; 
using Microsoft.SharePoint.Client; 

namespace StefanG.Tools 
{ 
    class CopyPeopleColumn 
    { 
        // helper method to lookup a user in the user info list 
        static string LookupLoginNameInUserInfoList 
                              (ClientContext context, int lookupId) 
        { 
            var username = string.Empty; 

            var userInfoList = context.Web.SiteUserInfoList; 
            context.Load(userInfoList); 

            ListItem item = userInfoList.GetItemById(lookupId); 
            context.Load(item); 
            context.ExecuteQuery(); 

            loginName = item["Name"] as string; 
            return loginName; 
        } 

        static void Main(string[] args) 
        { 
            // add code to configure the credentials for SPO 
            string userid = ...; 
            string pass = ...; 

            // create the SecureString object for the password 
            SecureString password = new SecureString(); 
            foreach (char a in pass) { password.AppendChar(a); } 

            // create the SPO credentials 
            ICredentials spoCred =  
                new Microsoft.SharePoint.Client.SharePointOnlineCredentials(userid,password); 


            // read people and groups field from source list 

            // create a client context to the source site collection using the  
            // credentials created earlier 
            ClientContext ctx = new ClientContext("https://url-to-source-site/"); 
            ctx.Credentials = spoCred; 

            // get all the objects down to the list item we want to copy 
            Web web = ctx.Web; 
            ctx.Load(web); 

            List list = web.Lists.GetByTitle("Source List"); 
            ctx.Load(list); 

            // for demo purposes I assume an item with Id 1 exists 
            ListItem item = list.GetItemById(1);    
            ctx.Load(item); 

            ctx.ExecuteQuery(); 

            // read the user details from the people and group column 
            FieldUserValue fuv = (FieldUserValue)item["user_column"]; 

            // use the lookup id to get the login name from the  
            // user information list of the source site collection 
            string loginName = LookupLoginNameInUserInfoList(ctx, fuv.LookupId); 


            // copy the content over to the new list 

            // create a client context to the target site collection using the  
            // credentials created earlier 
            ClientContext ctx2 = new ClientContext("https://url-to-target-site/"); 
            ctx2.Credentials = spoCred; 

            // get all the objects down to the list we want to copy to 
            Web web2 = ctx2.Web; 
            ctx2.Load(web2); 

            List list2 = web2.Lists.GetByTitle("Workload Technology Contacts"); 
            ctx2.Load(list2); 
            ctx2.ExecuteQuery(); 

            // ensure that the user with the login name is populated into the  
            // user information list in the target site collection 
            User newUser = web2.EnsureUser(loginName); 
            ctx2.Load(newUser); 
            ctx2.ExecuteQuery(); 

            // construct the value of the people or group column for the user 
            FieldUserValue newValue = new FieldUserValue(); 
            newValue.LookupId = newUser.Id; 

            // create a new list item and assign field value 
            ListItem targetListItem = list2.AddItem(new ListItemCreationInformation()); 
            targetListItem["user_column"] = newValue; 

            // write back to the target list 
            targetListItem.Update(); 
            ctx2.ExecuteQuery(); 

        } 
    } 
}