So I just downloaded the latest build of the game (death_road_to_canada_kidney_update_41508.sh) but when I try to select Start (or Unlocks for that matter) nothing happens, I can still select the setting and the exit sign yet I can't play the game.

Hello
Normally: right click > property > Permissions > Allow the execution of the file as a program.
Close the window and the game is executable: "picture"

What is your configuration; Mint Cinnamon ; Manjaro KDE ?
Funny; Death Road to Canada is a 32-bit executable according to: pcgamingwiki
And a 64-bit executable for Linux according to GOG: this game comes with a 64-bit binary only

It's not clear from your question whether you're having trouble running the downloaded installer or the game.
--

(1) Following up on LinuxFire's comment, if you're having trouble running the installer, yes, it's usually not marked executable on download and that bit must be set. You can also set it executable from the command line and/or run it with bash:

cd ~/Downloads
chmod +x death_road_to_canada_kidney_update_41508.sh
bash ./death_road_to_canada_kidney_update_41508.sh

Once installed, the game's start.sh script is typically already marked executable (though it's worth checking).

(2) If the installer completed successfully and you're not able to start the game, run the startup script in a terminal and paste the output log here for further troubleshooting assistance -- it usually comes down to a missing library (SDL2 most commonly)

cd "$HOME/GOG Games/Death Road to Canada"
bash ./start.sh

(The above assumes that's where you installed the game. Adjust accordingly.)

(3) Lastly, you could be talking about the actual in-game home screen -- as in, it started up but clicking the in-game menu options doesn't work.

This could stem from a number of possible input-related issues. Posting a terminal log may still be useful. If it doesn't respond to mouse input I'd say try swapping in and out of FullScreen mode -- as sometimes that offsets the in-game mouse cursor location. Only other suggestion I have on hand would be that I've always played the game with a controller... so if you happen to own a compatible gamepad, you might want to give that a try, as its cursor control won't be based on mouse coordinates.

LinuxFire's right, though, it would be immensely helpful for troubleshooting to know your software setup.

Operation 2 well explained by xixas. thanks for the help
Allows to launch the game, and also to see what happens...
The message obtained indicates that you are not at the right place.
To know the way to our position : ls -a

Maybe new on Linux, it's easier in graphic mode ?
Go to the game folder, located in the folder called "GOG Games" : YOU / GOG Games / Death Road to Canada
Open the terminal here with a "right click" > "open in terminal", you are now at the right place to place the order :
bash ./start.sh
------------------------------------------------off-topic-----------------------------------------------------
glxinfo | grep OpenGL
You can do this command to know your version of Mesa, often called to update by the after-sales service GOG.
I wonder if they also ask Rolling Release users this would be fun?
------------------------------------------------on-topic-----------------------------------------------------
Death Road to Canada Requires two libraries, user Manjaro you know the following: pacman -S .....
libsdl2-2.0-0
libsdl2-mixer-2.0-0

1)------------------------------------------------------------------------------------------------------------
~/GOG Games/Death Road to Canada >>> bash ./start.sh
Running Death Road to Canada
file open failed: No such file or directory

The game actually runs but only to the main menu, can't start the game.

2)------------------------------------------------------------------------------------------------------------
OpenGL vendor string: X.Org
OpenGL renderer string: Radeon RX 580 Series (POLARIS10, DRM 3.39.0, 5.9.11-3-MANJARO, LLVM 11.0.0)
OpenGL core profile version string: 4.6 (Core Profile) Mesa 20.2.3
OpenGL core profile shading language version string: 4.60
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 4.6 (Compatibility Profile) Mesa 20.2.3
OpenGL shading language version string: 4.60
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 20.2.3
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
OpenGL ES profile extensions:

3)------------------------------------------------------------------------------------------------------------
Dependencies are all met:
linux-vdso.so.1 (0x00007ffee81fb000)
libSDL2-2.0.so.0 => /usr/lib/libSDL2-2.0.so.0 (0x00007f5872892000)
libSDL2_mixer-2.0.so.0 => /usr/lib/libSDL2_mixer-2.0.so.0 (0x00007f587286f000)
libGL.so.1 => /usr/lib/libGL.so.1 (0x00007f58727e9000)
libGLU.so.1 => /usr/lib/libGLU.so.1 (0x00007f5872774000)
libm.so.6 => /usr/lib/libm.so.6 (0x00007f587262e000)
libc.so.6 => /usr/lib/libc.so.6 (0x00007f5872465000)
libdl.so.2 => /usr/lib/libdl.so.2 (0x00007f587245d000)
libpthread.so.0 => /usr/lib/libpthread.so.0 (0x00007f587243b000)
libGLdispatch.so.0 => /usr/lib/libGLdispatch.so.0 (0x00007f5872384000)
libGLX.so.0 => /usr/lib/libGLX.so.0 (0x00007f5872351000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x00007f5872174000)
libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x00007f587215a000)
/lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x00007f5872a42000)
libX11.so.6 => /usr/lib/libX11.so.6 (0x00007f5872017000)
libxcb.so.1 => /usr/lib/libxcb.so.1 (0x00007f5871fed000)
libXau.so.6 => /usr/lib/libXau.so.6 (0x00007f5871fe8000)
libXdmcp.so.6 => /usr/lib/libXdmcp.so.6 (0x00007f5871fe0000)

Strangely enough last version worked without problems.

You mean a problem only with the latest version of the game "KIDNEY" of 2020?
Did the "HUMERUS" version of 2018 work well for you?
https://www.gogdb.org/product/1960384075#changelog
In this case, we need to contact the developers.

Where before a Manjaro update?
In the second case, I'm still looking, but I think I need help, xixas are you an archer?
:-)
I don't see any error in the return of the Terminal.
May be a graphics driver problem ?
Possible to have the return of this command, just to be sure:
lspci | grep VGA

Is there a way to download the older versions of the installers? I apparently replaced my backup with the newest one.

I find it extremely odd, as it is the first time I encounter a problem like this (the game launching but not being able to start it).

No Sorry, not to my knowledge.
I have to understand that the old "HUMERUS" version works well?
http://www.rocketcat-games.com/

Same problem here.

./start.sh
Running Death Road to Canada
file open failed: No such file or directory

the error already happens immediately when launching the game. Though game seems to run fine. Except I am not able to enter game from game menu.

OS: Manjaro Linux
GPU: RX 5700 XT
Kernel: 5.10.0-1
GPU driver: amdgpu

Identical on Linux Mint 20, KIDNEY does not work:
I downloaded and installed the latest version of Death Road to Canada "KIDNEY"
The game starts, we access the menu, but pressing START doesn't do anything?

I have the same error with bash ./start.sh:
Running Death Road to Canada
file open failed: No such file or directory

I'm also experiencing this issue. I can see the main menu and options menu, but clicking START or UNLOCKS doesn't do what it should. The game reacts to the clicks with sounds and button animations, but still sits at the main menu.

FWIW "file open failed: No such file or directory" message seems to be related to opening ~/.madgarden/DR2C/gstats.save, and doesn't actually matter (I have that file from an older version of DR2C and tried to run the game with or without it and it yields the same result).

Same here
@Kepa-Rocketcat
Good luck finding the bug.

I do find it strange that such a basic action as starting the game did not trigger a failed test during the acceptance stage of development, before a version is released into production and replaces the previously available current version.

Any news?