Hi there, I'm running Plasma 5.13.5 with KF5 5.50.0 on a fresh installation of openSUSE Tumbleweed. The Audio Volume settings advanced option for "Automatically switch all running streams when a new output becomes available" did not automatically switch the running streams for me. I added the switch-on-connect module to the global PA configurations, and it works correctly, but I think it would be far better if the user could enable it with a simple checkbox. Thanks a lot!
Sad but true. :( See also Bug 392117.
This is fixed in Plasma 5.17!