You’re not going to break anything by trying all the options on that menu. How did it go?
About that thread you linked citing ‘works for me (wfm) on arch’ has nano /etc/modprobe.conf/myfile.conf where modprobe.conf reads files in the child directory /etc/modprobe.conf.d/. Maybe try that with the right sub-directory to force the iGPU to send sound over your HDMI card?