PowerShell script to get the list of all the SharePoint site collection administrators in the tenant

you can try this modified script

$Creds = Get-Credential

  $site = ‘https://tenant-admin.sharepoint.com’

Connect-SPOService -Url $site -Credential $Creds

$AllSites= Get-SPOSite -Limit All

$users = @();
foreach ($Allsite in $AllSites)
{

$AllUsers = Get-SPOUser -Site $AllSite.Url -Limit all | select DisplayName, LoginName,IsSiteAdmin
$users+=$AllUsers
$AllUsers = $null
#Write-Host $AllSite.Url" completed"

}
$users | Export-Csv -Path "C:\Users\Desktop\allusers.csv" -NoTypeInformation -Force

$Data = Import-Csv "C:\Users\Desktop\allusers.csv"

foreach($aUser in $Data)

{

  if($aUser.IsSiteAdmin -eq “True”)

  {

    Write-Host $aUser.DisplayName $aUser.LoginName

  }
  }