From a list of google groups (the group addresses), fetch corresponding member emails for each and write them to a gSheet, each group occupies a separate column

gGroupMembersToGSheet.gs

// Note: API must be enabled before use. 
// the person running the script needs to authorize the script AND from an email address that is listed as an administrator or owner on the group.

function main(){
  
  // Destination sheet of members
    var ss = SpreadsheetApp.openByUrl('SOMEURL');
  
  //array of emails; here I fetch them from the a named range in the above spreadsheet, but they could be hardcoded as an array
  var groupEmails = ss.getRangeByName("listOfGroups").getValues(); 
  
  // Where you want to output the list member emails, each group name outputs at the column header, with each corresponding member below that.
  // There is NO implied relationship between cells in adjacent columns.
  var membersDestinationTabName = "feed";
  
 // source and destination ss are the same
  getData(ss,groupEmails,membersDestinationTabName);
  
}

function getData(ss,groupEmails,membersDestinationTabName) {
  
  // TODO: wipe existing data from the sheet.
  // TODO: add time trigger to do this 2x a day
  
  Logger.log(groupEmails);
  
  // this is a bit kuldgy but I am not certain how to iterate over column addresses in A1 Notation
  var headerCols = ["A","B","C","D","E","F","G","H","I","J","K","L","M","N"];  
  
  // WRITE HEADERS
  for (i = 0; i < groupEmails.length && groupEmails[i]!=""; i++){
    var range = ss.getRange(membersDestinationTabName+'!'+headerCols[i]+'1');    
    range.setValue(groupEmails[i]);
  }
  
  //  WRITE MEMBERS FOR EACH GROUP
  for (var i = 0; i < groupEmails.length && groupEmails[i]!= ""; i++) {
    var GROUP_EMAIL = groupEmails[i];
    var destinationAddress = membersDestinationTabName+'!'+headerCols[i]+'2';
    
    var users;
    var request;
    
    try {
      var group = GroupsApp.getGroupByEmail(GROUP_EMAIL);
      users = group.getUsers();
      Logger.log(GROUP_EMAIL);
      
      
    } catch (err) {
      // TODO: scope error more tightly
      // When we can't fetch the users, it is generally a permissions issue; the output text to sheet could be changed if desired, but I don't want the program to crash for it
      users = [""];
    } 
    
    request = {
      range: destinationAddress,
      majorDimension: 'COLUMNS',
      values: [users], //still 2D
    };
    
    //API must be enabled before use. 
    //https://developers.google.com/apps-script/advanced/sheets
    Sheets.Spreadsheets.Values.update(request, ss.getId(), request.range, {
      valueInputOption: 'USER_ENTERED',
    });
    
    // otherwise we get timeouts for too many calls in a time period
    Utilities.sleep(3000);
    
  }
  
  
}