Hello SharePointers,

Below are the power shell scripts to enable external sharing in Modern Hub site

param
(
    [Parameter(Mandatory=$true)]
    [string]$HubSiteUrl,
    [Parameter(Mandatory=$true)][ValidateSet("Disabled","ExistingExternalUserSharingOnly","ExternalUserSharingOnly","ExternalUserAndGuestSharing")]
    [String]$ExternalSharing
)
 
$HubId = (Get-SPOHubSite -ErrorAction SilentlyContinue | Where {$_.SiteUrl -eq $HubSiteURL}).Id.Guid
if ($HubId -eq $null)
{
Throw "Not a Hub site "
}
 
$sites = Get-SPOSite -Limit All
foreach ($site in $Sites)
{
$siteDetails = Get-SPOSite $site.Url
If ($siteDetails.HubSiteId.Guid -eq $HubId)
{
Write-Host  $site.Url " external sharing permissions to " $ExternalSharing
Set-SPOSite $siteDetails -SharingCapability $ExternalSharing
}
}

Happy SharePointing Folks 🙂