ritogames.com should have been the official one
As someone who works on that site: Yes.
(Edit: By that site I mean riotgames.com)
This thread was added on February 06, 2020, with posts from Cashmiir.
Original Post
https://support-leagueoflegends.riotgames.com/hc/en-us/articles/360042302074-Claim-Your-Free-League-of-Legends-Refund-Token-for-2020-Here-