We have one of the customer who has all the mailboxes hosted in Exchange online.
I have ran few powershell commands to get the details of Litigation hold, Archive and License details and it showing Litigation hold enabled for F1 and E1 licenses also.
As per the MS Litigation hold supports only for E3 licenses.
I used this command: "get-mailbox -resultsizeunlimited | select DisplayName,PrimarySmtpAddress,RecipientTypeDetails,HiddenFromAddressListsEnabled,SKUAssigned,DeliverToMailboxAndForward,ForwardingSmtpAddress,ForwardingAddress,LitigationHoldEnabled,LitigationHoldDuration,InPlaceHolds,MailboxPlan,AccountDisabled,ArchiveStatus | Export-csv C:\Userlist.csv"
That's correct, but there's a difference between "supported" and "will actually work". Microsoft does not enforce licensing requirements for many functionalities, holds included. However, putting a mailbox on hold without the corresponding license is still a violation of the license terms.