I found a discussion on GitHub which helped me resolve the problem.
I added the two environment variables mentioned in the discussion to the machine scope and restarted the PowerShell Universal service. CPU usage has now returned to normal levels and monitoring with Process Monitor confirms the messaging system is disabled (as seen by dashboard processes no longer constantly polling the log files).
[Environment]::SetEnvironmentVariable('DBATOOLS_DISABLE_TEPP', $true, 'Machine')
[Environment]::SetEnvironmentVariable('DBATOOLS_DISABLE_LOGGING', $true, 'Machine')