Hello SharePointers,

Below are the powershell script to enable External Sharing in Modern Communication Site in Office 365.

Connect-SPOService -Url https://laksinnovation-admin.sharepoint.com

Set-SPOSite -Identity https://laksinnovation.sharepoint.com/sites/Communicationtestsite -SharingCapability ExternalUserAndGuestSharing

Happy SharePointing Folks!