yeah! it’s a pretty common practice these days. 4MS, Make Noise, NLC, noise Reap, Bastl, Worng, Insturo, bubblesound, Mobenthey, & many DIY projects use this method of using FR4 as a substrate for the panels.
the gold in this panel is metal, it’s the copper layer in the board. I recommend opening the files in kicad and taking a look for yourself.
Eurocircuits is a good option. All the China board houses should be able to handle this. It’s not that anything crazy is going on here, there are 3 layers. the Mask, the screen, and the copper which you can see all of in that panel, these are the same materials that are used for making any circuit, just used in a way other than to make electrical contacts / traces.