SelfControl -- The Linux port is described as 'Linux port of the Mac OS X application SelfControl . Uses Perl/Gtk2 + iptables. Provides basic timed blocking of specified hosts' and is an app in the network & admin category. There are more than 50 alternatives to SelfControl -- The Linux port for a variety of platforms, including Android, Mac, Windows, iPhone and Google Chrome apps. The best SelfControl -- The Linux port alternative is Mindful : Focus & Screen Time, which is both free and Open Source. Other great apps like SelfControl -- The Linux port are LeechBlock, DigiPaws, Cold Turkey and Plucky.
Easy set up, and most distractions (for me anyway) are online so it has good coverage