> OS updates spontaneously reset your default browser back to Edge
I've never seen this happen, and I have Chrome as default. I noticed the other issues you point out, but this never happened to me the years I've been dual-booting with Windows 10.
I suspect they are A/B testing it. A relative’s computer I help maintain did not replace Firefox as a default, but it did replace a PDF reader default (SumatraPDF iirc) with Edge, and on the next PDF double click - when Edge opened - it did a bunch of other things like logging in to Microsoft.
I've never seen this happen, and I have Chrome as default. I noticed the other issues you point out, but this never happened to me the years I've been dual-booting with Windows 10.