Backer from 2018, Is Steam version included?

I backed the game a few years ago. Wanted to see how the updates have treated it.

Is access over steam via our backer account possible?

Game was lit hard + cool last time I was zooming over the world map and getting medusa mind controlled.

You need separate code for Steam. If you backed early enough you should get an e-mail with selection if you want Steam or GOG key. And after that you should get Steam key. If you missed e-mails about that then you probably need to wait for @Valygar responce. Unless you are not entitled for the Steam key.