I would seriously guess near zero. People who use Edge are, I would guess, the types of people that just use the default, the people who do not know tech and just know which thing to click for "the internet".
Maybe nobody uses the default anyway and they just type "google" into the bing bar before they do any searches.
If they can trick a user just once into going "okay fine", the Google installer runs and now Google's managing your defaults for everything else. Which is why obviously Microsoft tries so hard to prevent installers from taking over the default browser setting now.
I regularly encounter users who have actively malicious search providers and entire web browsers they do not know how they got. Tricking people into changing over is very much a thing, and actually how Sundar became as popular as he is.
People often forget that Sundar Pichai's entire claim to fame at Google was the Google Toolbar, which was snuck into Flash Player and Reader installs to hijack people's search provider. (The same bundled install trick was, of course, then adapted to growth hack Chrome's numbers as well.)
Vertical Tabs and Chromium without Chrome, what's not to like. Oh, and the ChatGPT sidebar.