Ubuntu 18.04 - Steam installation trouble

[realpapazulu*****]

I had Steam running on Ubuntu 16.04 through 17.10 without problems. I did the update to Ubuntu 18.04 as a fresh install and cannot properly install Steam since then.

Setup:
- Tuxedo XUX707 laptop, RAM: 32GB
- CPU: Intel Core i7-7700 (-MT-MCP-) arch: Skylake rev.9 cache: 8192 KB
- Graphics: GeForce GTX 1060 Mobile, driver: 4.6.0 NVIDIA 390.48
- Monitor-Setup: 1x 4K builtin, 2x 1920x1080 external

Installation method 1: per apt/commandline from standard repos

sudo apt install steam

results in:

Die folgenden Pakete haben unerfüllte Abhängigkeiten:
 steam:i386 : Hängt ab von: libgl1-mesa-dri:i386 (>= 17.3) soll aber nicht installiert werden oder
                             libtxc-dxtn0:i386 ist aber nicht installierbar
              Hängt ab von: libgl1-mesa-dri:i386 soll aber nicht installiert werden
              Hängt ab von: libgl1-mesa-glx:i386 soll aber nicht installiert werden
              Empfiehlt: nvidia-driver-libs-i386:i386 ist aber nicht installierbar
E: Probleme können nicht korrigiert werden, Sie haben zurückgehaltene defekte Pakete.

This or similar error messages are well documented in earlier versions of Steam (around 2015) but none of the fixes works for me in Ubuntu 18.04, as the missing packages cannot be found or installed.

Variation: attempt to install steam-installer per Synaptic is not possible (error message about broken packages).

Installation method 2: Download of .deb from Steam website and installation per Ubuntu-software

First start of Steam brings up the terminal with message

Steam needs to install these additional packages: 
libgl1-mesa-dri:i386, libgl1-mesa-glx:i386

and then an error message before the launcher stalls.

Installation method 3: Flatpak version per Ubuntu-Software

This version works quite ok. The only game so far that will not launch is EXAPUNKS with error

Error: You are missing the following 32-bit libraries, and Steam may not
run:
libGL.so.1
libdrm.so.2

Anyone else with experiences/solutions for Steam on Ubuntu 18.04?

[Frank Guertler]

as far as i know you have to use the command line in a terminal like this:

sudo apt-get install steam

i dont know linux very much, but without "get" it should not work imo.

[realpapazulu*****]

There is no difference in the outcome between

sudo apt install steam

and

sudo apt-get install steam

[realpapazulu*****]

EXAPUNKS is running now after todays Steam update.

So, the flatpak version of Steam is now running on my machine without any currently known issues and seems to be the favourable way to install Steam on Ubuntu 18.04.