Comment 2 for bug 1889468

Apparently it's not just us, this is an upstream change. Dave Jones found this: https://www.raspberrypi.org/blog/latest-raspberry-pi-os-update-may-2020/

To select headphones, the recommended process is now to create a file called .asoundrc in your home dir with these contents:
defaults.pcm.card 1
defaults.ctl.card 1