Don't see it anywhere... signing up for an account is asking for a "Key"

K, found out you can't get the key in Galaxy... have to go to the game in your library on GOG.com and find it there

thanks for the info
its stupid it askes for key though

Did you figure out where the key was? I'm having trouble with this too

For whose the first post did not help, here the step-by-step instructions :
- Log in on the GOG.com website
- Go to your Profile then Games (the "Library")
- Left clic on Frozen Synapse 2, a menu will appear below the nameplate
- On the menu "More", select "Serial key"

Voilà :)

Edit : Added screenshot and better "wording"

Oh durr. Thanks a whole lot!

You're welcome, I did not find it at first : I was looking everywhere on the GOG Galaxy interface (where it should be, honestly)

Have fun and keep your VATs safe ^^

Yah, for real... devs said on their Discord they're looking into an option for Galaxy users to not have the need for a Key