Fonts on my main Linux "workstation" may not be as perfect as on the M1 Mac I use from the couch but it's because my 38" monitor ain't retina and it's a far cry from making "browsing uncomfortable".
Yes, many of the CSS stacks (even for the big sites which really should know better) are totally broken when it comes to Linux (they don't list enough fonts that various distro will have by default, they list fonts that many distro will not have by default and unsurprisingly end up defaulting to shitty fonts) and as soon as one site started using that one CSS stack, they all started the copy/pasta. But I wouldn't go as far as saying that browsing on Linux is "uncomfortable": many people do that on a daily basis and are perfectly happy.
Also not all websites have broken CSS font stacks for Linux. Some saw the light.