Stumbled over that last week. There is a company where I buy nearly all my computer stuff from, and I’m a customer for more than 20 years.
I wanted to order parts for a high-end PC, but simply could not add the motherboard to the shopping cart. Everything else was already in there. I called them, and they asked me if I used Firefox. And they told me in no uncertain terms that Firefox was dead and would no longer be supported for “safety and security reasons”, I should use Chrome or Edge instead.
If their site is too stupid to cope with Firefox, why the heck does it not tell me about this upfront, e.g. when I try to enter an item into the shopping cart?