@Vaj2 :-
I am, I guess, something of a "junior".....compared to some of our members. "Only" been using Linux exclusively for around 11½ years!
Y'know, in all that time I've never once come across a single web-site or online service that I couldn't access. Never yet been refused access to anything because I was running Linux. And in recent years, it's just gotten better......because NOW there's a whole load of additional websites that are offering online versions of their services.
A browser is OS-agnostic (with the exception of what the user-agent reports, though most folks are more concerned with how up-to-date your browser is). Platform, it seems, is largely irrelevant. It's a far cry from the days when most websites were "optimized" for Internet Exploder.....and if you weren't running Windows with an up-to-date IE, you could forget it.
You'll notice, too, that many desktop Linux 'clients' these days are identical in appearance and operation to the online version. You can thank
Electron for that, because what you now run on the desktop is essentially a transplanted "webapp".....powered by a minimal, stripped-back Chromium browser running only the essential components needed for online connection and interaction with that one website.
I've run Chrome/Chromium & many of the 'clones' (like Opera, Vivaldi, Brave, Slimjet, etc) since Chrome/Chromium first appeared in 2007. And the thing I like best about them IS the ability to turn ANY website INTO a desktop "webapp".....along with the ability to add Menu entries, etc, which lets you fire them up by themselves. Just like you would with a purpose-built desktop app/client.
I don't think you need worry about the future of Linux. As Brian ("Condobloke") says above, Linux has had the server market sewn up for years. The web runs on Linux, as do every single one of the Top500 supercomputers in the world. And Linux adoption is slowly yet steadily growing, largely due to M$ continually shooting themselves in the foot with so many of their daft decisions.
Nah, the future - for Linux - is looking quite "rosy".
Mike.