You are missing the following 32-bit libraries, and Steam may not run: libc.so.6

Assuming libc.so.6 is the only one you are missing, open a terminal and execute the following commands to install the missing library (be careful here and do not accept changes unless you are happy with the changes ie may uninstall stuff you want to keep!!):

sudo apt-get update
sudo apt-get install libc6-i386

Please post any errors.

If like me, mchid answer didn't solved your issue, try making a symlink to libc.so.6 and reinstalling steam from steamcmd:

find /lib -name libc.so.6
ln -s /lib/i386-linux-gnu/libc.so.6 /lib/libc.so.6
mkdir ~/steamcmd2 && cd $_
wget http://media.steampowered.com/client/steamcmd_linux.tar.gz
tar -xvzf steamcmd_linux.tar.gz
./steamcmd.sh

Then

./steam.sh

As of time of this post, using Ubuntu 20.04 LTS, I first tried installing using steam_latest.deb from their website, but got the OP error.

To resolve I ran this in terminal:

sudo apt-get install steam

And it would work after.