To get this game free of charge, all you have to do is download GOG GALAXY and create an account. After that, go to the “Recent” view and check the banner at the top. Click the giveaway button if you agree to receive news, updates, and GOG offers. After a while, the game will show up in your game library.
This means you are ready to join Geralt of Rivia on his epic adventures!
Symphonia is also available for free on GOG now. You can also get it on Itch.