Headphones "work", but only system sounds play

I'm using a new install of Ubuntu 26.04. Now, my headphones don't automatically work when plugged in, which isn't an issue as I'm used to open pavucontrol to force audio through the headphones (and by the way, they display as unplugged by default). And whenever I plug them in, sound does seem to work, but only system sounds . Firefox? No sound. Games on Steam? No sound. Trying to play an audio…