Despite the fact that Epic Games has pulled the plug on the UT4 master server, the community has saved the day! Led by timiimit with the development of a new master server alongside his UT4UU add-on, a large number of hubs and players have already made the switch.
If you are interested in connecting your UT4 install to the community master server, go to the UT4 Master Server website, create an account and follow the instructions from the menu in the upper right corner of the page: http://ms.getut4.com/
Also on the website, in addition to install instructions, there is a very handy listing of all of the current UT4 matches being played.