As a Linux user this has got me very worried. Chromium has so much market share that this change will certainly go through, and I feel like Safari won’t care as it benefits them and their ecosystem to have device checks. I feel like Firefox and non standard OSes will almost certainly be blocked on a large range of websites with little impact on total users, not to mention completely blocking ad block and anti-tracking clients.
I think eventually regulators in the US will file an antitrust lawsuit and break chromium off of Google if this actually happens, but until then Fediverse/FOSS and personal websites are going to be the only places untouched by this.