Inspiron 5675 with AMD 570 issues

It is not a lemon.

The 2017 AMD Radeon RX 570 is a great video card for modern monitors that have DP or Mini DP or HDMI. That is the market we are going for with this 2017 computer and video card. These newer video cards were not designed thinking of older monitors that only have VGA and DVI ports.

"The AMD Radeon RX 570 is one of the latest graphics cards from AMD for desktop PCs, targeting the enthusiast level gaming market. Radeon RX 470 delivers rich and immersive VR experience with advanced comfort and effortless compatibility with VR headsets."

Even the 4GB AMD Radeon RX 570 scores well.

AMD Radeon RX 570 Specifications

GPU = AMD Radeon RX 570 Polaris 10 PRO
Bus Type = PCIe 3.0 (16 lanes)
Graphics clock = 926 MHz (base), 1206 MHz (boost)
Memory clock = 1650 MHz
External Connectors = Three DP 1.4 HDR ready, HDMI 2.0
Memory interface = 256-bit
Bandwidth: 211GB/s or higher
GDDR5 = 8GB
Resolution = 4096x2160, 32bit color
Ambient temperature = 0°C to 45°C
Recommended system power (W) = 500w
Graphics card power (W): 150w average

Simply put there is no way to get 2 displays to work with this card.

Incorrect. I can think of six ways to attach two monitors to this video card.

(1)
AMD Radeon RX 570 DP out port --> DP to DP cable --> #1 monitor DP in port
AMD Radeon RX 570 DP out port --> DP to DP cable --> #2 monitor DP in port

(2)
AMD Radeon RX 570 DP out port --> DP to mDP cable --> #1 monitor mDP in port
AMD Radeon RX 570 DP out port --> DP to mDP cable --> #2 monitor mDP in port

(3)
AMD Radeon RX 570 DP out port --> DP to DP cable --> #1 monitor DP in port
AMD Radeon RX 570 DP out port --> DP to mDP cable --> #2 monitor mDP in port

(4)
AMD Radeon RX 570 DP out port --> DP to DP cable --> #1 monitor DP in port
AMD Radeon RX 570 HDMI out port --> HDMI to HDMI cable --> #2 monitor HDMI in port

(5)
AMD Radeon RX 570 DP out port --> DP to mDP cable --> #1 monitor mDP in port
AMD Radeon RX 570 HDMI out port --> HDMI to HDMI cable --> #2 monitor HDMI in port

(6)
AMD Radeon RX 570 DP out port --> DP to HDMI cable --> #1 monitor HDMI in
AMD Radeon RX 570 HDMI out port --> HDMI to HDMI cable --> #2 monitor HDMI in port

'The 2017 AMD Radeon RX 570 is a great video card for modern monitors that have DP or Mini DP or HDMI. That is the market we are going for with this 2017 computer and video card. These newer video cards were not designed thinking of older monitors that only have VGA and DVI ports.'

Really?

Listen very carefully...I just bought two (2) new monitors that have connections for 2 HDMI  cables and 1 VGA. Nothing for a 'display port'...In fact, nobody anywhere seems to sell anything for this 'display port' stuff some folks are pushing. In fact, I had to buy two (2) HDMI to 'display port' converters that were REDUCED in price cause a big name store wanted them gone - nobody else wanted them. Dust collectors. Had I known the video card had only one (1) HDMI slot I would not have bought the PC. This card is history - I will replace it very soon. In your jovial statements you talk of using 'display port' cables which do not exist. Even the guy at Gamestop had a big laugh over this cause he doesn't sell any of this stuff, by choice. Wait until I show him just how easy it is to use if only such cables existed!  Don't know and don't care about DVI or VGA. Not an Issue. The card is fine. Just the limited use cause of a lack of HDMI connections in favor of something nobody seems to know about or even care for.

I cannot speak to the Gamestop employee lack of knowledge about current hardware.

Dell offers many monitors with DP or mDP ports.

DP to DP cables

DP to mDP cables

DP to HDMI cables

mDP to HDMI cables