Hey there @unreal_toon_learner! Welcome to the community! So I’ll drop you a couple of personal favorites. I personally recommend the material based ones instead of mixing in post processing, because it’s more viable for multiple platforms and (usually) less expensive.
Disclaimer: These links are to external tutorials by members of the community not affiliated with Epic Games. This said, you are liable for anything that occurs beyond this Unreal Engine domain.
Post Processing Based Cel Shading: https://www.youtube.com/watch?v=GQhdbH8O7Oc
Material Based: https://www.youtube.com/watch?v=Z4ur9c8H6AI
A thread where a community member came very close to perfecting a really nice one. Probably better as reference since the pop in for range is less fun. Material-based cel-shading with support for multiple light sources
The engine team has a pretty strong focus on the tech side of things usually, getting extra content in usually comes in as templates. Otherwise many users never end up using or seeing them. I thought one of the old content examples had a cel shaded material, but I could be wrong on that.
Hope this helps and happy creating!