After checking the patch notes and seeing it patched in so it will always appear at Hanged Man's Tree, I loaded up my save (in front of Hanged Man's Tree), looted Zoltan Chivay and... nothing (except telling me I've got a Gwent card, as if this were the tutorial message). The quest "Collect 'Em All" is still not complete, and the achievement will not pop. I've tried loading the save again, fast travelling to another spot in Velen, then riding back to Hanged Man's Tree and looting again to no avail; tried a second time with meditation.
I've used multiple checklists online to check my collection, there are definitely no more cards remaining for me... is it possible this achievement is bugged and won't pop if this patched-in card is the last I collected?
As much as I enjoyed Gwent, I wanted my second playthrough to be solely focussed on beating Death March...
---------- Updated at 01:05 AM ----------
Further to this, I just tried reloading the save, then fast-travelling to Skellige and back (thinking I might need to reload all of Velen): now the Hanged Man's Tree only has the "Unfinished Book" and no Zoltan card... so I guess we're back to the original problem, 1.07 didn't fix this issue at all?