I'm on Ubuntu 20.04.3 LTS, on a thinkpad T480. I just bought a new TV, and would like to use it to play audio/video from my computer, over HDMI. Video works fine, but I can't seem to get audio working. I know it's not a problem with the TV or the cable, because my nintendo switch works fine. I don't think it's a problem with my computer's sound card, because I've played sound over HDMI in the past (with a monitor, not a TV). When I do aplay -l the HDMI output is not even detected; I get

**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC257 Analog [ALC257 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

Any ideas? what commands should I run to gather more information?

EDIT: here is the output of sudo lshw -c video:

  *-display                 
       description: VGA compatible controller
       product: UHD Graphics 620
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 07
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:160 memory:e7000000-e7ffffff memory:c0000000-cfffffff ioport:e000(size=64) memory:c0000-dffff