Looking for means to block apps/websites during certain hours of the day (pc, mobile)

The one Discord group I'm in is often most active after midnight, it is the biggest reason I stay up till 2 AM, which is terribke when I will have to start getting up at 6 AM when studying starts. Hexbear and Lemmygrad also become time sinks for me.

So what are recommendations for applications that can block apps and websites?