itch.io

I got the email too :)
Thank you very much !

I'm in the same case of you (I've bought the game last year). On the discord it's write :

Christian | Producer20/08/2020

@everyone Regarding the question "If I bought an early version of Griefhelm on Itch.io, will I receive a Steam key?"

Griefhelm is not the same game now that it was then. So much has been added - replayable campaign, online multiplayer, new weapons/armor/maps/gamemodes, post launch support, etc. BUT with that being said, we want to show our admiration and support for those who showed us admiration and support at the very beginning. We are standing by our claim and plan on sending Griefhelm Steam Keys to everyone who previously purchased the game on Itch.io. If you are one of Griefhelm's early supporters - expect to see an email from me either tonight or tomorrow with a Steam key. We love you and can't wait to see you in Griefhelm tomorrow.

But I have never got a key currently. So i think it's only for the first buyers ... I really appreciate the game, it's very fun to play with friend but I will not pay the game again.