> Because if it's hard when targeting Chromium and adapting to {Safari,Firefox} but easy when targeting Safari and adapting to {Chromium,Firefox} then honestly it seems like Chromium is the problem.

Exactly. Test and develop against Firefox and/or Safari first and Chrome afterwards. If it’s not a true web standard and isn’t widely implemented, don’t use it.

The web worked fine for decades without smart fridge integration or whatever weird thing Google has decided that browsers must be capable of most recently.