Update, read here:

https://alexholmeset.blog/2018/06/09/is-office-365-groups-pre-prepared-for-teams/

If you use the Microsoft Teams PowerShell module you can only get a list of teams your a member of, even if you are a global admin. With this little script you get a list of all Office 365 Groups and whether its Teams enabled or not. It checks if the group’s mailbox contains a folder type named TeamChat. At first i did a check if there was a folder in conversation history that was named “Team Chat”, but got a tip from Tony Redmond that this changes based on the mailbox language

$TeamsTrueFalse = @()

$Groups = Get-UnifiedGroup

foreach ($Group in $Groups){
$TeamsEnabledCheck = Get-MailboxFolderStatistics -Identity $Group.Alias -IncludeOldestAndNewestItems -FolderScope ConversationHistory | Select-Object FolderType

If ($TeamsEnabledCheck.FolderType -like 'TeamChat') {

$TeamsEnabled = $true

}
else {
$TeamsEnabled = $false
}

$Object=[PSCustomObject]@{
'Group Alias' = $Group.Alias
'Teams enabled' = $TeamsEnabled

}#EndPSCustomObject
$TeamsTrueFalse+=$Object

}

$TeamsTrueFalse