This app was mentioned in 2 comments, with an average of 1.00 upvote
I have used this when I got my achievement. But I used my phone a lot more when looking up gwent cards and this site isn't mobile-friendly.
https://play.google.com/store/apps/details?id=za.co.redcode.w3c
I used this checklist app, easy on the eye, it can also divide the cards into factions and locations. Also has checklist for other things on Witcher 3.
I used an android app to track all the cards.