Nope.
Viewing post in Vae Victis - Khan (0.13 latest) comments
Perhaps I misunderstood (and please understand that I'm an inexperienced Steam developer so I might be wrong here): if you bought it on Itch, you don't need to buy it again if you want to download and play on your computer or phone. However, if you want a Steam version for your convenience, you will have to buy it again on Steam.