How do I configure my traction control in Le Mans Ultimate?

Agreed this article doesn't explain. The answer is somewhat in game in the garage adjustment section shown in one of the photos:

ONBOARD TC
For newer cars, which have an updated TC (Traction Control) system, this option controls the longitudinal slip (similar to wheel spin).

ONBOARD TC POWER CUT
The amount of power that is cut when traction control activates. Only available for the updated TC system. This option may be linked to the 'Onboard TC' so that this option cannot be controlled individually.
This level can also be adjusted dynamically when driving when available.

ONBOARD TC SLIP ANGLE
Controls how much slip angle (lateral side-slip) is allowed before the traction control activates. Only available for the updated TC system. This option may be linked to the
"Onboard TC" so that this option cannot be controlled individually. This level can also be adjusted dynamically when driving when available.

Just shows where to edit, but no explanation of those three different TC types. Pretty useless unfortunately.

so useless explanation

Perfect 3 point simple description. If you don't know what basic racing terms like traction, slip angle etc then you may want to look them up.

Yeah some explanation of how the setting interact with each other and what settings to try depending on what you are trying to achieve. Tradeoffs between setting high and low values, etc.

I agree with MiskoRacing. I'm knew to these concepts and really have no idea what these settings do.

This is not explaining a thing about what different traction control setting actually do.