[chrismartin]

"What are you doing with your weird broken browser, you weirdo?"

(I am also a weirdo)

Fun fact, Slack also started blocking Fierfox 78 ESR last winter, which was the default browser in Debian stable until just a couple of weeks ago. They don't merely show an unsupported browser message, but actively prevent the app from loading. It still worked fine if you spoofed the user agent string to report a later Firefox version. It felt like unnecessary hostility to users for no actual security benefit.