The versions of Virtual Audio Cable floating around have an annoyance - Trial.
Go to sound devices in devmgmt.msc and uninstall.
Earlier versions don't have this sound.
Hard to track down!

I know what's new by observation.
Defender runs all the time.
In some cases it will reach 50% of the cpu on a dual core.
Seems to be triggered during some reboots or forever after once triggered,...

I have found the servers written for linux servers seem to last longer after installation so I use them for webmail / email servers. But there are things to be done with Windows that it does a better...

Sort of, I can boot a virtual machine while hyper-v is enabled, however,
there are still issues.
*if the vm has a server such as iRedMail running in an ubuntu 20.04 vm,
it boots and runs and...