Why? Chrome is such a terrible browser to begin with. How is it a deal breaker?

I can't speak to the GPs reasons, but Chrome has a large enough user-base that anyone building for the web is going to want to at least test their work in it.

In my own experience, Chromium browser (which is the base for Google Chrome) works much better (faster) than Firefox on my Pinebook Pro (ARM, Linux).

But I think the author is using Chrome under emulation, so bad performance is expected.

Correct, I didn't grab the ARM Chromium build, only Chrome. If you want to avoid using Edge then Chromium or Firefox is the way to go.

Given edge is just a chromium wrapper, why avoid it? Just ecosystem issues? (Password managers, etc?)

I don't avoid it, but some people do because it's a Microsoft product, as is tradition.

As if those will come any time soon. The big ARM scare of 2017 is already over. ARM is not competitive. By the time they catch up in the server and laptop markets, RISC-V will have eaten their lunch. All they have left to do is run marketing campaigns against RISC-V and watch their inevitable decline.

2033 the year of RISC-V on the desktop?