Firefox doesn't implement the AudioData API, which is probably necessary for the waveform viewer and cropping tool Discord presents in the soundboard management UI.
I’m a little baffled by this one. File upload isn’t exactly some new HTML5.1 feature or anything. There’s no good reason they can’t have this handled properly.
There's really no reason to be mad at them in this particular instance. Their client is Chromium-based (Electron) so they will optimize their new features for that engine first. There's probably less than 5% users who Discord from browser, let alone Firefox, and I think I'm being generous with that number. Additionally, some things are harder to implement (or even impossible) in native web rather than Electron, that has all the NodeJS integrations.
I tried to use lyft on my computer yesterday to download a receipt for my expense report, it didn't let me, kept telling me to download the Android app...