The short story is, no, there isn't one particular brand when selecting either a GeForce or Radeon graphics card that a Linux gamer/enthusiast should go with over another AIB partner. Over the past 12 years of running Phoronix, there has been no single AIB partner that superbly stands out compared to the rest when it comes to graphics card AIB partner brands like ASUS, Zotac, HIS, MSI, etc. They all work under Linux, rarely the AIB differences extend beyond the heatsink/cooler and any default clock speed differences, and I haven't seen one that's over-the-top crazy about Linux. I also haven't seen any major partner consistently put the Tux logo or other Linux markings on their product packaging, let alone incorporate any Linux drivers onto their CD/DVD driver media.
The question from readers posing questions along these lines usually then becomes who I would select or who is most supportive under Linux. In regards to the AIBs that I have dealt with currently or in the past when it comes to Linux graphics card testing -- where the representatives knowingly supply graphics card review samples for Linux enthusiast/gaming type testing are as follows:
While NVIDIA is usually the company sending out new launch-day GPU samples directly, a long-time partner for NVIDIA Linux testing on Phoronix has been EVGA. They have sent out samples for Linux testing for more than a decade and are also one of the most popular and most well known NVIDIA partners. Also having supplied samples for Linux testing over the years has been MSI and ASUS and Gigabyte and ECS back in the day.
On the AMD Radeon side, the most prolific partner for Linux testing has traditionally been Sapphire. While they used to supply a ton of graphics card samples, I haven't seen any since the Northern Islands days from them. ASUS and MSI have also supplied samples here in the past although I haven't been in touch with ASUS in a few years. Years ago there were also some Linux testing samples from Diamond.
Those are the main NVIDIA/AMD partners that come to mind if you're wanting to try to find the company helping to support Linux the most. Feel free to share your own personal graphics card board recommendations via the forums.