I think Firefox is being sabotaged.
Over the past couple years, I keep encountering operational failures in Firefox that are not present in Chrome or any other browser.
A few weeks ago, a website ( https://investor.vanguard.com/home/ ) started returning "Unable to open [site]. Cannot locate the Internet server or proxy server." This is not a problem for Chrome, which opens the page almost instantly. Before that, the site wouldn't let Firefox log in after, literally, years of uneventful browsing there. In 2020, the login failure started, but didn't last long.
Earlier, I was at eBay, AliExpress & Etsy; each link took upwards of a minute to open and eBay's pages weren't loading images unless I started clicking in a non-random, but still experimental manner.
I'm using 105.0.1 (the latest, according to the popup).
If it matters, my OS is Windows 7 Pro.