https://wccftech.com/free-ffvii-remake-ps5-upgrade-ps-plus/

Square Enix has announced that those who own the PS Plus version of Final Fantasy VII Remake will be able to upgrade to the PS5 version for free after all. 

Back in March of this year, Final Fantasy VII Remake joined the PS Plus library of free titles for subscribers. Unfortunately, those who claimed the game via Sony's subscruption service weren't able to upgrade the game to, then upcoming, PS5 version of the title - this option was only available to those who purchased the PS4 version of the title.