As a dcp-o-matic user from 2017, I used it successfully for generating DCP for my short films, it is really a nice tool !
However on my relatively old computer, it was not posssible to play the DCP in real time before to check it in a cinema.
Thus, I developped my own free and open source player, in a beta state for PC and Windows 10 (or Ubuntu)
It requires an Nvidia GPU with a Pascal or more recent architecture.
It is also limited to 2k DCP, with stereo or 5.1 soundtrack, and optionally subtitles, unencrypted.
It as been tested on Geforce sucessfully 1060, 1080, 2070 (smooth 2k full resolution playing on 1080p screen, and real time 2k to 4k upscaling on 4k TV)
It can be usefull for independant filmmakers, and can be seen as a complementary tool to Dcp-o-matic.
Don't hesitate to test it.
Binaries for Windows are provided. Just download the main zip file, and uncompress it before running "FreeDcpPlayer.exe"
For geeks : C++ source code is provided, with Visual Studio project for Windows and makefile for Linux.