https://www.gamespot.com/articles/last-chance-free-legendary-pokemon-for-august-stil/1100-6460839/

A new month is underway, which means another pair of free Legendary Pokemon are now available for Pokemon Ultra Sun and Ultra Moon. This time, The Pokemon Company is giving away the Ruby and Sapphire cover monsters Groudon and Kyogre as part of its ongoing Year of Legendary Pokemon promotion, but as usual, you'll only have a limited time to grab them. [Update: The deadline for grabbing these freebies is coming up fast, so make sure to get them while you still can.]

As with previous distributions, the way to receive the Legendaries differs depending on where you live. Once again, US residents will need to travel to a specific retailer to pick up a free download code for the Pokemon. This time, the code will be available at participating GameStop stores from August 3-26. Pokemon fansite Serebii reports that players in the UK will need to travel to Game stores to get the code.