List all Site Collection Admins Powershell

# ONEDRIVE SITE MANAGEMENT

# Assuming you have the SPO/PnP modules installed from MS already, found here:
# https://docs.microsoft.com/en-us/powershell/sharepoint/sharepoint-online/connect-sharepoint-online?view=sharepoint-ps
# https://www.microsoft.com/en-us/download/details.aspx?id=35588

# Uncomment the "Install-Module"s if you haven't already installed the modules in PS after installing them to your machine using the links above.
# Install-Module -Name Microsoft.Online.SharePoint.PowerShell -ErrorAction Stop
Import-Module -Name Microsoft.Online.SharePoint.PowerShell
# Install-Module SharePointPnPPowerShellOnline -ErrorAction Stop
Import-Module SharePointPnPPowerShellOnline

$365cred = (Get-Credential)

# Get PersonalUrl of a OneDrive site
$upn = 'john.doe@domain.com'
$tenantName = 'domain-admin'
Connect-PnPOnline -Url "https://$($tenantname).sharepoint.com" -Credentials $365Cred
$url = (Get-PnPUserProfileProperty -Account $upn).PersonalUrl
Disconnect-PnPOnline

# or 
# Manual override if siteUrl known
# $url = "https://$($tenantname).sharepoint.com/personal/john_doe_domain_com"


# Get information about a OneDrive site incl. SiteCollectionAdmins 
# (requires personalUrl)
Connect-SPOService -URL "https://$($tenantname).sharepoint.com" -Credential $365Cred
Get-SPOSite -Identity $url -Detailed | Format-List
Get-SPOUser -Site $url -Limit all | Select-Object DisplayName, LoginName, IsSiteAdmin | Sort-Object IsSiteAdmin, DisplayName | Format-Table -GroupBy IsSiteAdmin -AutoSize

# Add a user to site owner access
Set-SPOUser -Site $url -LoginName "upnOfUserToAdd" -IsSiteCollectionAdmin $true

# Remove a user from site owner access
Set-SPOUser -Site $url -LoginName "upnOfUserToRemove" -IsSiteCollectionAdmin $false