From first tests with the
StarTech USB3DOCKH2DP I just bought, I can say that all 3 external monitors are working fine, even with the notebook display enabled:
https://photos.app.goo.gl/s5p6UEZcY5nW5Jnf8
The difference here is that is an older model which use only the USB3.0 port and not like the newer model which uses the USB-C port.
From Control Panel of Windows I can see that
3 monitors are managed by the external station (instead of 2+1 like other model) and only the built-in monitor is managed by the internal Intel chipset.
Also, just for test purposes, while the dock was connected I attached 2 additional displays on the built-in HDMI port of the notebook and on the built-in USB-C port of the notebook (with a simple adapter), and all 6 monitors are working correctly.
And in this case, 3 monitors are managed by the Intel chipset and 3 monitors are managed by the external station.
https://photos.app.goo.gl/T3P83vCFZzhnmH3FA
After all this tests and this success, I'm willing to consider an USB-C incompatibility problem or something related to the notebook hardware or Windows drivers.
I will try a couple of days with this station but for the moment is seems the problem to be finally solved.