Edge is not free. I wouldn't seriously consider using a non-free application for something as essential as everyday web browsing.
You can't really have usable vertical tabs in Chromium via plugins either, unless you're content with wasting a lot of horizontal space for an ugly sidebar and vertical space for uselessly duplicated tab bar.
Firefox is the only actual choice I'm aware about.
Using Firefox definitely supports the existence of a free browser. Loss of market share is the #1 threat to the continued existence of a free browser. Beyond the obvious (if a tree falls in a forest, crushing the last copy of the code for a browser that has zero users, then was it a browser at all?):
lower market share =>
nobody testing against the free browser or fixing site breakage =>
quirks (bugs, underdefined specifications, nonstandard features) of other browsers becoming required for a functional Web =>
free browser is no longer a browser of the actual Web.
Given that the issue of Firefox being forced to restart primarily happens on Linux, I doubt Edge is an option for them. Though I have to concur that Edge has one of the most stable and smooth vertical tab implementations around, most of the plugin-based ones are more fully featured but much less reliable.
I use it, and it's decent. And more in the vein of "it's not google" though I do slightly prefer the chrome dev tools to the modifications that Edge has made. I don't like a lot of the "helpers" for shopping though. And definitely don't like the article wall with ads that are really hard to block/script out.
You can't really have usable vertical tabs in Chromium via plugins either, unless you're content with wasting a lot of horizontal space for an ugly sidebar and vertical space for uselessly duplicated tab bar.
Firefox is the only actual choice I'm aware about.