I solved the problem [partly, as shown below] myself.
After having installed via USB I compared the settings in detail.
Here is what I did, Swedish UI (guessing on English wordings):
1. Open Inställningar/Settings, Enheter/Units (BT, printer, mouse).
2. For the Envy 4520 (network) click Hantera/Manage.
3. Select the Enhetsinställningar/Unit settings tab.
4. Select Automatic configuration, Verkställ/Apply, and OK.
And now printing works like a charm.
FYI: I also added a standard TCP/IP port.
Somewhere here I unplugged the USB cable.
However: I just noted one EXTRA HP Envy 5420 (Network) with status 'Driver missing' (Drivrutin saknas). This seems connected with the scanner part, driver by Microsoft. HPPsdr could not locate the printer.
So, I switched back to the WSD port. Result: scanning works, but printing is back to the no-color/no-duplex state.
When I receive your confirmation of reading this I will be happy to start a remote access session.
Thanks for your (continued) efforts!
Tommy