Comment by gamesieve

https://gamesieve.com/

An alternative front-end / game discovery service / price tracker for GOG's catalog. Mostly manually enhancing the data from the API (90% heuristics, 10% human effort, as the total dataset isn't large enough for it to be worth doing otherwise), and offering a wider range of filters for it all.

I'm grouping all related products together for a more complete overview, and have recently added library import, where I mostly 'solved' the issue of GOG not recognizing that you own certain games if you got them as a freebie or as part of a since-delisted deluxe edition. Just now starting in on incomplete "series" listings, seeing what'd be involved with making them contain all relevant games, and then exposing that.