After trying out multiple USB-C docks, I have found a cheap and reliable solution which supports the specific features I need for my living room. These are my requirements:

1. Full support for HDMI 2.0, i.e. 4K60Hz and HDR10 support. Many USB-C hubs only support 4K30Hz, or don't support HDR over HDMI.
2. Allows the use of a USB-C extension cable, specifically one that is 3ft long. Extension cables are not part of the USB-C specification yet, but some docks still support them.
3. Uses all 4 differential pairs of the USB-C cable as DisplayPort lanes. The more lanes that are used for DisplayPort, the longer the extension cable can be (and more reliable).
4. Disables USB devices when the computer is disconnected. Bugs in this process frequently cause Ethernet packet storms, as evidenced in exhibits: [A, B, C]
5. Properly implements USB-C Power Delivery (>30W). Some docks incorrectly advertise the wattage of the power adapter without subtracting its own power consumption.

I've finally stumbled upon the solution: the uni USB-C 4-in-1 Hub with a UGREEN 3ft USB-C Extension Cable. I bought them on sale, and the total cost including shipping was $22 + $11 = $33 USD. This is the current listing for the USB-C Hub:

And this is the current listing for the USB-C Extension Cable:

The setup works great with my 4K TV. I simply connect the 3ft long USB-C cable to my MacBook in clamshell mode. Attached to the USB 2.0 port on the other end is a Logitech Wireless Keyboard dongle, and a Plugable Gigabit Ethernet Adapter for reliable internet. In Display Preferences, macOS recognizes the HDR capabilities of my TV and lists multiple Retina resolutions.

Upon testing, the dock correctly reduces the advertised USB-C PD rating from 60W (adapter) to 56W (dock). It uses all 4 pairs in the USB-C cable for DisplayPort, which does limit us to USB 2.0 speeds on the USB port. When I disconnect my MacBook, it properly disables the ethernet adapter (stopping packet storms) and disables the wireless keyboard adapter (saving power). Overall, I'm very pleased with this cheap and reliable setup.

Hall of Shame

• The Apple USB-C to HDMI dock did not support the 3ft USB-C extension cable and uses only 2/4 lanes of the USB-C cable for DisplayPort.
• The Cable Matters 4k60Hz dock did not support HDR and caused packet storms which brought down my entire network.
• The uni USB-C 8-in-1 dock I previously reviewed does not support HDMI 2.0, and caused packet storms as well.