Presumably they just either haven’t made a proper package for opensuse, or their platform detection isn’t perfect. Since Debian based distros are the most common, sometimes companies will only distribute Deb files…
In any case, I’d personally recommend getting steam via flatpak, it works quite well.
Heck yes! I like to read in my terminal, and the go fonts are one of the best monospaced serif fonts I’ve found for the purpose