I could of sworn I read Sony decided to make the PSN account optional.
I just searched it, straight from playstations website:
https://direct.playstation.com/en-us/buy-games/god-of-war-ragnarok-pc
“Do I need a PSN account to play PlayStation games on PC?”
“No, you currently do not need a PSN account to enjoy PlayStation Studio games on PC, but you will need a Steam account to redeem your voucher code. Some of our PlayStation Studios titles also offer incentives for linking your Steam and PSN accounts.”
Edit: Their website could be outdated, or incorrect? I just swear I saw an article title that Sony removed the requirement for PSN for Ragnarok PC.