Apparently some games require libssl.so.1.0.0 which is not part of the steam native runtime of Solus and as a result they will not launch anymore using the native runtime.

The bundled runtime works ok as it includes the library:

/.local/share/Steam $ find . -name '*ssl*'
...
./ubuntu12_32/steam-runtime/lib/i386-linux-gnu/libssl.so.1.0.0
./ubuntu12_32/steam-runtime/lib/x86_64-linux-gnu/libssl.so.1.0.0

Examples of games I own that fail to start:

• Baldur's Gate
• Tomb Raider
• Planescape

All of the above error out with similar missing library errors like this:

/home/user/.local/share/Steam/steamapps/common/Tomb Raider/bin/TombRaider: error while loading shared libraries: libssl.so.1.0.0: cannot open shared object file: No such file or directory

Installing the package manually fixes this and all of the above games run successfully in the native runtime as well:

$ eopkg li | grep openssl-32bit
openssl-32bit                               - 32-bit libraries for openssl

It was suggested in this reddit discussion that a bug report be raised to consider inclusion of this library as a dependency of the native runtime.