Why not? Chromium (= Blink, plus some other stuff like a network request stack) development happens in the open, just like WebKit development. It might be steered by Google to such an extent that there's always the possibility of it going in a bad direction; but it's not like you're not going to hear about it if something privacy-violating is introduced into the Chromium codebase (rather than the downstream Chrome codebase.) And you can switch away from the browsers that use it if/when that happens.
For that matter, if upstream Chromium ever did start "going bad", those browsers that rely upon it would also likely switch away from it, either cooperatively forking it into a new community-maintained project, or switching over to WebKit (with which it is still mostly ABI-compatible.)
> browsers with such tiny market share that they'll never be tested against, and sites will routinely be broken for you
Even if you don't want to use anything based on Blink, WebKit is also a large ecosytem, and minor WebKit-based browsers can "inherit compatibility" from developers targeting (mostly Mobile) Safari. Several Linux browsers (GNOME Web, Falkon, Midori) use WebKit, for example. They render everything just fine (i.e. just like Safari does.)
> The browser also sends unique hardware identifiers to Microsoft, which is a "strong and enduring identifier" that cannot be easily changed or deleted.
https://www.bleepingcomputer.com/news/microsoft/research-fin...
Yes, I can see why you'd avoid Edge specifically, same as avoiding Chrome specifically.
But that's not an argument against using upstream Chromium (which is, in fact, a browser all on its own, stadnalone downloadable and shipping with several Linux distros); or against other Blink/Chromium-based browsers (e.g. Brave), no? Either choice would get you compatibility with anything Chrome itself is compatible with (in terms of websites; not necessarily in terms of extensions—though the difference is just in the legacy Chrome extension APIs; WebExtensions work fine everywhere.)