Not being able to use Firefox for banking or finance is something that hasn't happened to me in years. When it did happen, it was usually fixed with a simple workaround of sending a custom user agent string.

I think e.g. Capital One is using Wasm, yuck. That needs to be enabled (it is by default in Firefox).

Ah... I use Chrome on Linux, and it works just fine for banks and credit cards.

Same. It's exceptionally rare for Firefox to fail me and force me to use a different browser. I'm when it does happen, it's either a Chrome specific feature, or a failure of the developer.

It's not (just) Firefox to blame. It's ramp.com, mailgun, and these other big apps that don't bother testing on Firefox. You can't even login on these