So I’ve had my doubts if the upgraded expansion worth the price and purchased the basic version thinking I’ll be able to purchase the additional upgrade later (it was presented in the available DLCs list). Of course, a hour of research later I’ve decided to get the better version and suddenly the “Ultimate upgrade” item has disappeared from the available DLCs on Steam. I guess these are the same payment team shenanigans as there were during the November launch when people were unable to get their coin packs purchased on Steam.
Fix maybe?
edit: there is new option appeared, within the game’s shop UI and I’ve managed to grab the upgrade. Although it displayed an error (53xxxxx) somehow but I can access all the stuff in the package. Happy end.