What are your thoughts on coding challenges in the interview process? Also differentiating between a project with a few days of time to solve it, or and onsite challenge while coding during the onsite interview.

I have to admit I like it. The reason when they ask such things they already want me to do actual tech-work and not just talk and "manage" stuff.

Onsite interview is better. You get to notice their body language, comfort level, thought process, questioning and reasoning abilities.

More importantly, I never like to ask them do a full project kind of test. Anybody can do that given the time and freedom. It is those nitty-gritty niche areas and corner cases that makes the whole experience interesting and worthwhile