I thought I bought a defective motherboard as it appeared to have corrosion but it was fine. What wasn’t fine was that the audio was cracking in KDE and Gnome 46 would only have audio using the front panel and not the back. This is not ideal as the front panel is ideal for headphones and the back for speakers (impedance too high, case location).
Now that I’m back in Gnome 47 the problem persists. The solution:
Using alsamixer to change ALSA controls
sudo alsamixer --card=1
→ to locate ‘Auto-Mute Mode’ and ↓ to change to ‘Disabled’
← to Locate ‘Front’ output and raise volume ↑ to 100 ‘Front’
Special thanks to @nikgnomic for the solution.