Thanks for your opinion, but it is not going to change our policy or our sales page. Just like the unsupported macOS, any issues encountered in Linux OS would not be troubleshot by Dell. All they could do is perform basic monitor hardware troubleshooting like the stand alone BID (Built-in Diagnostics).
HI All, This is a continuation of this topic mentioned below where Chris from Dell provide the solution:" none of the Dell D/E/G/P/S/SE/Alienware monitors have macOS support from Dell" . I cannot find any official DELL statement about this. The topic/thread mentioned by Chris has been deleted as well. That is strange, because DELL on the product page does not mention about incompatibility with Apple notebooks - so that is not fair.  In addition I have been using P2219HC for long time without issues but once switched to QHD version of "the same monitor" the background/grid flickering appeared. I know many people also who are using P series monitors without any issues with M1 MacBook. So I believe that could be some resolution / firmware upgrade which can fix this annoying issue.  Dell could you help please? Could you even compere P2219HC vs P2421DC in case of color profiles etc. please ?Related topic:  P2422H, MacBook Pro M1, flickering grid   
P2421DC, MacBook M1 flickering grid