I have a laptop running Ubuntu 18.04 64-bit. I joined GOG recently looking for Linux-supported video games. I bought 6 of them and was frustrated when I attempted to download and install one of them. After marking the installer as executable, I launched it through the GUI and was met with an error right off the bat saying that a file couldn’t be found. The file does exist, but I can’t find the folder it says it should be in. I was running the file “mojosetup” figuring that was the installer file. I also attempted running “start.sh” and was faced with another error, indicating a necessary file named “ libcrypto.so.1.0.0” didn’t exist.

failed to load file 'data/noarch/docs/installer_readme.txt' (Mojosetup)

jbh@jbh-HP-EliteBook-2560p:~$ sudo bash '/home/jbh/Desktop/Undertale/start.sh'
[sudo] password for jbh:
Running Undertale
./runner: error while loading shared libraries: libcrypto.so.1.0.0: cannot open shared object file: No such file or directory
jbh@jbh-HP-EliteBook-2560p:~$ (Terminal start.sh)

Why not install it then?

sudo apt-get install libssl1.0.0

It looks like you're missing at least one library... check the game's store page for names of the packages you may need to install. For 32 bit packages you should be able to get most of the ones you're likely to need by simply installing the ia32-libs package.

Also, Why are you trying to run it as root?

If a game has Linux support, be sure to check system requirements. It will note any packages you need to install in addition to the game. In your case, Undertale needs the following packages installed before you can install the game to your system:

libc6:i386 libasound2:i386 libasound2-data:i386 libasound2-plugins:i386 libcurl3:i386 libgtk2.0-0:i386 libopenal1:i386 libglu1:i386 and dependencies (libssl1.0.0 is likely one of the unlisted dependencies as you need it).

You can install these packages through the Ubuntu Software Center or your preferred package manager, or via the command line. If you only need libssl1.0.0, then just run the command given by loki1985 above.