As reported today by Juli Clover at MacRumors, Apple is now allowing iCloud Photos users to transfer a copy of their data to Google Photos. This joins the growing suite of tools provided on Apple’s Data and Privacy webpage, which also include downloading copies of your data, correcting your data, and deactivating or deleting your account.
As described in a new Apple Support document on this topic, the iCloud Photos transfer process does not delete your photos and videos from iCloud, it just copies a duplicate of the data to Google Photos. Clover notes:
The transfer process takes between three and seven days, with Apple verifying that the request was made by you. To do the transfer, you must have two-factor authentication turned on for your Apple ID account and you must have a Google Photos account with enough storage to complete the transfer.
Further details over at MacRumors.