You can buy either:
The GameShell only needs the WAD files you get after installing Doom on your PC.
Also you can buy:
The Hexen Collection also contains Hexen II. See my post below how to get that running!
The GameShell has the following chocolates out of the box 
:
This is for games based on a DOOM engine (including Hexen).
Hexen II however uses a modified Quake engine.
So, steps for Hexen II:
sudo sed -i -- '/^deb .*stretch main$/ s/$/ contrib/' /etc/apt/sources.list
The /etc/apt/sources.list should now look like this (assuming you have not yet set the repo to your own country):
# deb http://debian-mirror.sakura.ne.jp/debian/ stretch main
deb http://debian-mirror.sakura.ne.jp/debian/ stretch main contrib
deb-src http://debian-mirror.sakura.ne.jp/debian/ stretch main
deb http://security.debian.org/debian-security stretch/updates main
deb-src http://security.debian.org/debian-security stretch/updates main
# stretch-updates, previously known as 'volatile'
deb http://debian-mirror.sakura.ne.jp/debian/ stretch-updates main
deb-src http://debian-mirror.sakura.ne.jp/debian/ stretch-updates main
sudo apt update && sudo apt -y install uhexen2
mkdir -p /home/cpi/games/Hexen2/data1/
Copy your purchased pak0.pak and pak1.pak of Hexen II to that data1/ folder.
Create a launch script like this:
cd /home/cpi/apps/launcher/Menu/GameShell/
echo 'mkdir -p ~/.hexen2' > 'Hexen II.sh'
echo 'ln -s ~/games/Hexen2/data1 ~/.hexen2/' >> 'Hexen II.sh'
echo 'hexen2 -f -width 320 -height 240' >> 'Hexen II.sh'
echo 'unlink ~/.hexen2/data1' >> 'Hexen II.sh'
Please tell me the performance and how to get music in-game. 
Did you trie this ? https://www.moddb.com/mods/doom-slayer-chronicles/downloads/doom-slayer-chronicles-v10-full/page/2
I believe the GS can run this engine and textures, but I’m not shure what version of OpenGl GS has.
As far as I know the GameShell does not support OpenGL. I haven’t tried GZDoom (or even ZDoom). Why do you believe the GS can run OpenGL?
I followed the instructions and all I get is "IWAD file ‘/home/cpi/games/Doom/doom.wad’ not found!
Same for Doom 2. I am using the latest wad files I’ve had for over 20 years.
Pretty sure the files are in the right place.
It might be pwads and not iwads. Can’t share mine due to copyright.
Did some looking around online and found this converter utility. Haven’t tried it. Let me know if this helps.
In the hidden config file of chocolate-doom where can I remap the light key? I only know they are ‘H’, ‘Y’, ‘Shift’, ‘O’ and ‘L’. I would appreciate if someone explain me.
Where did you find your non-steam IWADS?
EDIT: I also would like to know how to rebind my controls for the game.
Steam wads work fine haven’t had any issues or problems
You are a god! now can you make shadow warrior work please master Oet
Works great, but talking about Freedoom, how we can choose the pahse 2, freedoom2.wad that is included?
I guess it is all possible. Making it work is never the issue. Working out the details and making it user friendly is. 
This is just a Build engine source port to make it almost similar to Shadow Warrior.
But the real sources have just been released last week?!
hehe ok I found it, just copied like with doom and heretic, same thing but to launch the freedoom2 wad 
Wow! I want it! 
How do you create the sh files?
Figured it out. I just copied the freedoom.sh and renamed it to doom and edited it.
Is there a way to increase the sensitivity of movement or make it faster? The turns are really slow.
Pressing Y during turns increases speed, right?
Thanks! Works great.
dude I think I I have a man crush on you every time I’m on the forum you make me gush! Your tutorials are so easy to follow! keep em coming!
Too bad you (or I) ain’t a gamer girl. 
First I wanna figure out what broke eduke32 before writing any new tutorials. 