I don't hear any sound on Kubuntu 18.04 LTS

Had the same problem, found a solution here on askubuntu and it worked for me! Ubuntu 18.04 audio disappeared after update

tomas reported that after adding a boot parameter to grub, their audio was restored. https://askubuntu.com/a/1218063/718497

So to answer my own question. After a lot of digging I finally managed to get my audio working again. After finding this thread https://bugs.archlinux.org/task/64720 I tried temporarily adding the boot parameter snd_hda_intel.dmic_detect=0 by following this guide: How do I add a kernel boot parameter? to verify that it worked. It solved my problem, and I added the key permanently now, and the fix seems to persist after reboot.

Please upvote tomas if it helps. :-)

(I would've posted this as a comment, but my rep isn't 50 just yet)