For some reason, when I try to navigate Fairphone official website from my phone, the sidebar just doesn’t open (or how it’s called, I’m not sure. The button I highlighted on the attached screenshot).
I can confirm English version of the webpage works as expected on Firefox in my phone.
So the problem is Vivaldi-specific. I’m not sure if I should redirect that problem to them or this is the problem with Fairphone webpage’s implementation.