Here is everything we have right now as resources go for Animation Rigging: Compilation of resources for Animation Rigging
Also, Unity Engine - Unity Discussions is the better sub-forum to ask questions on Animation Rigging.
Unfortunately, we haven’t published much content up to now using Timeline, but we haven’t seen any issue with the character rigs we have published up to now in a timeline setup.
I would suggest trying out first with the animation rigging samples and see if these work well in a timeline in your project.