Why not just display a warning and let me try anyway? How sure are they that their filtering out absolutely every device that can't run it successfully. Why risk denying it unnecessarily?
I think it checks for the APIs it needs, and bails when they are unavailable. Atleast, that’s what I feel given the brief flash of the application before the warning replaces it.
There are way more than dozens. In fact, it looks like Safari is (probably) ahead of Firefox on desktop: https://gs.statcounter.com/browser-market-share/desktop/worl... (9.1% Safari, 6.6% Firefox), https://www.similarweb.com/browsers/worldwide/desktop/ (7.6% Safari, 5.7% Firefox), https://radar.cloudflare.com/reports/browser-market-share-20... (scroll to "Market Share by OS" and select "Desktop"; Cloudflare is the one that shows Safari behind Firefox at 6.6% marketshare compared to Firefox at 7.2% - but also 39% of Mac users are on Safari, a highly valuable demographic given the higher-income skew of Mac users as well as the fact that a third of professional developers are on Mac (and only 47% on Windows according to Stack Overflow's survey)).
It would be worth spending a few minutes improving this notice. Give more context for what the heck this is, and distinguish between "your screen is too small" and "you're using a browser that doesn't have the API we need".
There's nothing wrong using Webkit / Safari on your laptop or desktop. There are dozens of us, DOZENS!