XPS 9310: headphone jack only outputs sound to one ear

I recently got a XPS 9310 and performed a clean install of Ubuntu 20.04.2 with the latest linux-image-oem (5.10). The hardware configuration is certified for Ubuntu 20.04, and the system works quite well overall -- thanks to the Project Sputnik people for helping to make Linux a first-class citizen!

My problem is that when I connect my headphones to the headphone jack, only the left earpiece outputs sound. Changing the output balance in system settings->sound doesn't help. Further, when I try to test the individual headphone speakers, the front right speaker remains completely silent. The headphones themselves work perfectly with my other Linux laptops, and the same problem occurs if I use a different set of headphones.

To make matters more confusing, the Dell BIOS diagnostics don't detect any problem.

Have any other users experienced this problem? Is there any software configuration that could possibly be at fault? Or does it smell like a hardware issue?