I can only assure you verbally that this is a great game. They made some major strides on it over the years and it is so good. Anyway, official open beta information is below.
SQUARE ENIX released a Lodestone post showcasing how to participate in the FINAL FANTASY XIV Xbox Series X|S Open Beta test, which is scheduled to begin on Wednesday, February 21 at 12:00am PST.
The open beta test will only be available to new players who will be playing FINAL FANTASY XIV for the first time. Players who already have the Free Trial version for a different platform or a FINAL FANTASY XIV license registered to their SQUARE ENIX account will be unable to participate in the open beta test. Fans can take this opportunity to invite their Xbox-owning friends who have never experienced the ever-expanding world of FINAL FANTASY XIV and adventure together!
Details on how to participate can be found on the Lodestone post here.