I am wondering if that is just my car colour without a clearcoat. (selinite grey) Be interested to know how it wears and what you have to do to look after it.
Being a bit old fashioned I like a bit of chrome so cannot help re dechroming. Whilst not directly relevant to the EQC mbworld.org which has a majority american readership has a huge amount of mercedes info across all models aapart from the EQC as it has never been exported there! Am sure you will find some general tips re mercedes de chroming as of course they transfer the same build techniques across all models. The GLCf forums may be a good place to look given our EQC are related.
I have seen a video on fitting the running boards on a GLC so it will show you how they are fixed if you were thinking of taking them off in the dechrome, they are an optional extra here in France and I did not spec them and for me the car looks better without plus it is easier to get in and out. On the test drive of a car with them I was swearing about them after half an hour🙄