The only browser that I think could make me switch is qutebrowser, though the lack of an adblocker is an obstacle for me.
Just kidding. I do not do this.
qutebrowser has a built-in adblocker (based on a host blacklist) which works fine for most scenarios.
There's also https://gitlab.com/jgkamat/jblock though that's not really supported until extension support is finished.
But great to know there's some progress.
I noticed this too in FF on Linux, I inspect elemented and for some reason a huge number of websites were using Nimbus Sans as the font... Later when I eventually used someone's Windows install I realized that Nimbus was only being used on my computer... Wtf?
It's a font developed long ago by some famous font foundry, and a subset covering common characters was made free and included in Linux printer drivers. It is visually very similar to Helvetica/San Francisco. I installed GNU FreeFont (probably available in your distro's repos) which looks the exact same but covers many more characters than Nimbus. In Firefox I went to the font config settings, set FreeSans/FreeSerif as the default fonts, and unchecked the option to allow websites to specify custom fonts. Just don't disable the checkbox to download web fonts, or icon fonts with various icons/glyphs will show as boxes.
It's truly beautiful - every once in a while I see some text and just stop reading and stare at it for a few seconds. On the rare occasion when I go to a website about fonts I use another browser to be able to see their CSS-specified fonts.