I just checked on the old notebook of mine, the runtime is broken yes.
- If you have a steam runtime desktop icon right click on it and open with kwriter
- Find
Exec=/usr/bin/steam-runtime %U
- Rename it to
Exec=/usr/bin/steam %U
- Save it
- Run steam from desktop
If you launch it from the start menu you can do the same, icon is located under /home/YOURUSERNAMEHERE/.local/share/applications
or copy the newly .desktop file over there.