This is now the second game on GOG, that's NOT WORKING on Linux (but it's avail for Linux). "libpng12.so.0" is missing. Well, i know, i can install that missing lib on my own, but honestly, why the fork im paying for it? As mentioned, this is the 2nd game on GOG, i have problems. The other game was announced as "with german language", but it wasn't avail. in german.

This really begins to make me angry! Get your stuff together, GOG!

How to fix on (K)Ubuntu 20.04:

sudo add-apt-repository ppa:linuxuprising/libpng12
sudo apt update
sudo apt install libpng12-0

for these problems I advised in my post similar to this one, to switch from the "sh" files that need dependency, to flatpak packages or appimage that should have the dependencies internally. It would be convenient because even in 5 years and more it won't we should look for the deprecated dependencies that are inside such packages, they are also installable on all distributions (they are both open source not as snap and its closed server controlled by Canonical!). What game is this package for (I'm curious) ?Is the game okay now?

Yeah... The Linux port is linked against versioned libraries and doesn't provide alternatives to the system-provided ones, so this game already has compatibility issues with the latest distros. These are the libraries we'll need to hunt down outside the default Ubuntu repos (output is a snipped run of ldd against the main executable):

libavcodec.so.56 => not found
libavdevice.so.56 => not found
libavformat.so.56 => not found
libavfilter.so.5 => not found
libavutil.so.54 => not found
libswresample.so.1 => not found
libswscale.so.3 => not found
libpng12.so.0 => not found

--edit--
I built libpng 1.2.59 and ffmpeg 2.8.17 (with support for libSDL 1.2), installed them into a directory on the side, and added that directory to LD_LIBRARY_PATH. That appears to be enough to get the game to start.

OpenAL doesn't seem to be totally happy, but it doesn't appear to have done caused any real issue so far. Perhaps I don't need HRTFs (Most likely this is an incompatibility with the most recent OpenAL version):

AL lib: (EE) AddFileEntry: Invalid header in /usr/share/openal/hrtf/default-44100.mhr: "MinPHR02"
AL lib: (EE) AddFileEntry: Failed to load /usr/share/openal/hrtf/default-44100.mhr
AL lib: (EE) AddFileEntry: Invalid header in /usr/share/openal/hrtf/default-48000.mhr: "MinPHR02"
AL lib: (EE) AddFileEntry: Failed to load /usr/share/openal/hrtf/default-48000.mhr
No HRTFs found
HRTF not enabled!

I think it can also work for you :

https://www.gog.com/forum/ken_folletts_the_pillars_of_the_earth_season_pass/patch_missing_libpng12so0_on_linux

Excellent info. Thanks vesinor.