Finally, Surabaya Inferno has been released in Steam in 20 September 2020. Soon you can get Steam keys from buying Surabaya Inferno 1.5 in this is site (more cheaper about 5.45 USD than in Steam, 6.99 USD).!

https://store.steampowered.com/app/1393810/Surabaya_Inferno/?beta=1