Hi Jude,
The 'Get-SPO' cmdlet should work for your needs. The SPO module should work for GCC low & high as it has selectors specific to GCC high.
Get-SPOUser -Site https://domain-admin.sharepoint.com | where {$_.IsGroup -eq $false}
Replacing 'domain' for yours. Scripting in each specific domain would give you the full list needed.
Here's some additional information towards scripting this fully:
[https://learn.microsoft.com/en-us/answers/questions/1276124/ps-script-to-check-what-sites-the-user-has-access
)
If this answers your needs please mark this as the correct answer!
-Mike Z