I just registered to let you know that the Quadro 4000 is not dead, yet.

It folds without issues under Linux (OpenSUSE Leap 15.2) using driver 390.141.
As you already mentioned, FAH 7.6.21 recognizes it as Mac Edition but I think that's only a naming issue in GPUs.txt because some time ago, it was recognized correctly as 'Quadro 4000'. In recent GPUs.txt the 'Quadro 4000' entry is missing and there's only the 'Quadro 4000 Mac Edition'. But that doesn't impact folding at all.
The issue of not being recognized by Windows 10 is something I cannot confirm, too. My workstation at work is also equipped with a Quadro 4000 and is running Windows 10 x64 without any issues in CAD applications. I just didn't try folding on this machine but I can't imagine why it shouldn't work. Driver version is 377.83, if I remember correctly, I can recheck on Monday.
If you really want to get your Quadro 4000s to fold, there are some pros and cons in my opinion:
(+) They're not as slow as one might think regarding their age, e.g. I have no problems with finishing before timeout even when folding only for a few hours per day
(+) They have a quite low GPU clock (as almost all Quadro cards) which means there's a quite high overclocking potential (mine are running at around 140 to 145 % stock clock rate)
(-) Compared with your 1050ti they are much slower and less energy efficient
(-) Their single slot cooling design is not very powerful, so they will run quite hot and / or loud, especially if not regularly cleaned. You can fit aftermarket cooling solutions as long as you check compatibility with a GTX 480 (done that myself). The only question is if you want to buy a cooler that costs the same or more than the market price of the card itself..
