MacBook Pro 13'' (2020) with Dell TB16
From GitHubs description:

Many people file bugs here about their Dell TB16 dock.
The USB, Thunderbolt 3, and audio out ports should regain
functionality after installing Thunderbolt 3 Unblocker.
However, video output does not work. Unfortunately, this is out of
scope for this project.

It clearly states that video output (e.g. HDMI) is not supported by this project.
They further clarify:

For whatever reason, an update to macOS High Sierra broke support for the displays attached to the TB16.

and also mention to upgrade the firmware of the dock:

You could try performing a firmware upgrade on the TB16, which has been reported to restore video (HDMI output). However, the firmware upgrade must be performed from Windows.


There is also a Thread about this issue on Apples own forums, suggesting to try this GitHub project, yet it is older and untested on newer hardware/software (i.e. make backups of your system and know how to revert these changes!).
You could try to reset SMC, NVRAM/PRAM and boot into safe mode.
You could try a clean install, but it looks like this specific Dell dock is finicky with Apple hardware.