Get SharePoint 2016 base language and language packs. For more details see: https://andikrueger.wordpress.com/2018/02/26/sharepoint-2016-base-language-and-language-packs/

Get-SharePointLanguages.psm1

#Requires -RunAsAdministrator
function Get-SharePointLanguages 
{
  $baseLanguageKey = Get-Item 'HKLM:\SOFTWARE\Microsoft\Shared Tools\Web Server Extensions\16.0\ServerLanguage'
  $baseLanguageValue = $baseLanguageKey.Property

  if($null -ne $baseLanguageValue -and $baseLanguageValue.Count -eq 1)
  {
      $baseLanguageCulture = New-Object System.Globalization.CultureInfo([int]$baseLanguageValue[0])
      Write-Host "SharePoint base language:" -ForegroundColor Green
      Write-Host $($baseLanguageCulture.DisplayName)
  }

  $languagePackKey = Get-Item 'HKLM:\SOFTWARE\Microsoft\Shared Tools\Web Server Extensions\16.0\InstalledLanguages'    

  if($null -ne $languagePackKey)
  {
      Write-Host "SharePoint Language Packs:" -ForegroundColor Green
      $languagePackKey.Property | ForEach-Object -Process {
          $languagePackCulture = New-Object System.Globalization.CultureInfo([int]$_)
          Write-Host $languagePackCulture.DisplayName
      }

  }
}
Export-ModuleMember -Function Get-*