https://wccftech.com/the-witcher-3-free-gog/

The Witcher 3 is now available for free on GOG if you own any other PC version or if you own it on consoles.

The offer, which will be available until June 23rd, will allow owners of the Steam, Origin, Epic Games Store, PlayStation 4, and Xbox One versions of the game to receive a DRM-free copy of the game. Just download the GOG Galaxy 2.0 client, connect your platforms, and claim your copy. Unfortunately, the offer is not available for Nintendo Switch owners.