So far, it looks like ASUS, Gigabyte, and MSI have joined NVIDIA's GPP. HardOCP did some digging and wrote an update about the situation. The site says it's hard to get information about this matter as everyone is afraid to talk about the GPP. However, Kyle Bennett did manage to confirm that Dell and HP are resisting the GPP:
Dell and HP not coming on board with GPP is actually a very big deal. Out of all the companies that we think NVIDIA is strong arming into GPP, Dell and HP have the most leverage to push back due to the massive volumes of mid and low-end GPUs that both purchase from NVIDIA. While AMD is not able to compete on the extremely high end, it certainly is making mid-level and low-end GPUs that both Dell and HP have access to. And for what it is worth, the Vega 64 is an excellent gaming card at 1440p which fits the bill for a huge portion of the market on high end gaming systems. NVIDIA may be in a fight to seize these companies gaming brands for their own, which NVIDIA may just lose, and hopefully so.HardOCP speculates that Intel may planning legal action against NVIDIA as the GPP also has an impact on sales of the Kaby Lake-G processors, which contain AMD-based graphics.
Dell nor HP are wanting to turn over their gaming brands to NVIDIA. Off the record conversations suggest that both of these companies think that NVIDIA GPP is unethical, and likely illegal as it pertains to anti-competition laws here in the United States. The bottom line is that Dell and HP are very much upset with NVIDIA over GPP, and Dell and HP look to be digging in for a fight.