The 5c image in my test share now has the patches RadxaNaoki linked (inc. the audio fix) above. The previous image only has the &hdmi0_sound node added, not the i2c node.
If gnarlsnishi confirms all is working I'll push a kernel/patches update to official LE nightlies. I've been holding off bumping the kernel to 6.18-rcX as there were PCI issues in the initial rc releases, but those seem to be resolved upstream now.
f1gogata no idea what the problem is but I've updated the branch with current patches and it works for me. NB: I'm building on an older Ubuntu 22.04.5 (LTS) host.