I have fiber here in my apartment.
There is an optical network terminal with an Ethernet port on it. The optical network terminal does not appear to do any routing, just conversion of the signal between the electrical and optical interfaces. An ordinary PC can be plugged directly into it, use DHCP to get its IP address, and that’s it.
I was supplied a router by the ISP as well. It’s spent the better part of the last decade gathering dust in a drawer.
Meanwhile, I’ve been using Firefox for ages and have never experienced the problems these people keep complaining about.
There was a brief time when Chrome ran better than Firefox on an old 512MB laptop I had, but Chrome has since become an infamous RAM hog. Firefox is the lightweight one now, and has been for quite a few years.
Good riddance to bad spyware.