There are several of these 'lousy" websites, here are just a few:
English description / Description en anglais
clegc-gckey.gc.ca
Apple, Asus, HP, and more.
www.theverge.com
Regardless of browser (FF or Chromium) these two font families are the problem. However, if I disabled them (by unclicking) they are fine. My system for whatever reason is blocking the files. I also added Arial and deleted Helvetica, the display is fine.
Both sites look good on my PC
Sorry about your messed up fonts
Can an undamaged font be copied into the font folder, and delete the damaged font file?
You might have to boot a live usb of linux to do that, dont know.
When the system prevents file changes, use a different OS to force the change
You can use Ventoy to easily boot an iso of linux, perhaps linux mint, Ubuntu or another one.
It will boot as a live usb. And most linux versions have a try it before install it option.
Some versions of linux can do it, and some live usb linux versions may block access to the c drive, but I have done this before, so I know it can work. ALL linux versions give full drives access after an install, in which case the PC would be dual bootable to either linux or windows.
Get a good copy of the font file, download it off some web storage place, delete the font in windows and copy in a good file
You can join a linux forum and ask about this.