For quite a while now, browsing websites in Firefox on my Linux setup has been quite uncomfortable:
It often took half a minute to load pages properly, despite having a decent internet connection and hardware setup.
So I looked up the issue, and found that Linux‘ proxy lookup may prevents the browser to connect to servers more quickly.
That being said, there was the recommendation to simply disable any proxy usage by default (this only works with a VPN-less connection though, of course):
Results were amazing. Websites do show up quickly again!