The problem still occurs on the latest stable PulseAudio packages (1:15.0+dfsg1-1ubuntu2.2) for Ubuntu 21.10. Also, doing a "pulseaudio -k" on the Terminal, and then restarting any software that was outputting audio, fixes the issue. I've noticed that this only happens after the output audio device is changed between the available devices. So, going from the "HDMI/DP3 output" to "Digital Output" and then back will cause the crackling after a few minutes.
The problem still occurs on the latest stable PulseAudio packages (1:15.0+ dfsg1-1ubuntu2. 2) for Ubuntu 21.10. Also, doing a "pulseaudio -k" on the Terminal, and then restarting any software that was outputting audio, fixes the issue. I've noticed that this only happens after the output audio device is changed between the available devices. So, going from the "HDMI/DP3 output" to "Digital Output" and then back will cause the crackling after a few minutes.