imessage
How to send iMessages on iPad without having own iPhone?
Question marked as
You can use your AppleID email address, or any email address listed under your AppleID as an alternate email address. You just cannot use a cellular telephone number as a send from or receive at address without an iPhone.
That does mean you cannot send or receive SMS/MMS messages without a cell phone. But iMessage is not a cellular telephone messaging service - it is an internet messaging service and can use your AppleID email as the send from and receive at address,
See this support document - Set up iMessage on iPad - Apple Support