What I would have done is tested it with an Android phone. My Samsung S26 Ultra allows me to connect to an external display via a USB C hub. So the test setup would be:

1. Plug the phone into hub.

2. Check that you get display output, the mouse and keyboard are working whilst the screen is not turned off and the phone is not locked.

3. Lock the screen and wait for the screen to turn off, thereby mimicking suspend.

4. Try to make the phone resume by using the attached keyboard and/or mouse.

If all goes well, the monitor should turn on after unlocking the phone or using the keyboard / mouse.

# Other things to try

Again try and reproduce the issue with a Samsung tablet that supports display out via USB C.

Connect the keyboard via Bluetooth and try to make the laptop resume. I found that connecting a Keychron keyboard via bluetooth allowed me to resume a Macbook Pro. I was kinda surprised that this worked.

Does the same issue occur on Linux as well?

I guess you could attach a USB packet type of debugger to ensure that data is being sent to the laptop by attaching the debugger to the cable that connects to the host machine. If you see USB traffic when the monitor goes to sleep and you are pressing keys in the keyboard and the dock still has power that means the dock is working fine so you can rule that out.

My Android Phone will connect to my dock and all connected hardware functions as expected but it doesn't charge the phone. After the first disconnect subsequent connections to the phone will just charge the phone but the phone does not detect the hardware connected to the dock. If I then remove the power cord going into the dock and connect the dock up to the phone then no hardware is detected but if I then proceed to insert the power cord into the dock the hardware connected to the dock starts working but the phone is not charging.

It's a cheap phone with a USB-C port that works at USB2 speeds and the dock uses display-link but go figure.