It works now, that wasn't the case last time I'd looked.
I wouldn't call it "absolutely fine" by any means. It's way too slow to render for me to use (took about 30 seconds to render the submitted link on my phone, mastodon took about 10 seconds to render a toot). I'm beyond sick of slow web pages.
The mobile web application worked about as well as it does today from at least my join date of April 27, 2023.
As for performance on my iPhone 15, on a 5G (not 5GUW) network, it loads in a second and a half; I just checked. I have some complaints with what RN does in terms of affordances but performance isn't a problem.
Admittedly, my phone (Pixel 3a) is a piece of crap. I just checked it on my Thinkpad on a gigabit connection. It still took about 10 seconds of that spinning circle to render the page content.
I wouldn't call it "absolutely fine" by any means. It's way too slow to render for me to use (took about 30 seconds to render the submitted link on my phone, mastodon took about 10 seconds to render a toot). I'm beyond sick of slow web pages.