Also on a Epic, the base game was free at some point

https://store.epicgames.com/en-US/p/vampire-survivors-vampire-survivors-emerald-diorama-9ac68f

Also available on Android where the base game is always free

https://play.google.com/store/apps/details?id=com.poncle.vampiresurvivors

Edit: I understand that some people prefer Steam, it’s not a reason to not provide alternatives for those who don’t care, so thanks for the downvotes, they weren’t necessary.