I started the game up on steam and was thrown into the laboratory with no explanation of anything. It looks like significant progress was made, such as 2/3 mutagens unlocked, not that I know what that means in terms of the game since I haven't played yet. Is there a way to delete progress on steam? As I've said I've NEVER played the expansion before, only regular gwent and thronebreaker.

Absolutely the same issue here and I found no way to reset the progress...

FYI: The game starts with you having 2/3 mutagens unlocked. It's important for the story. After you complete your first run and earn your first mutagen, you complete your first set of 3/3 and then you unlock the next cinematic. In short, the story begins after the main characters have already been doing a bunch of research and have found 2 mutagens before the game begins.