The Flatpak is not officially supported either and your proposed alternative is to use that instead of the i686 packages.
As a strong supporter of Flatpaks, it would be awesome if Steam was better supported there, but it architecturally can’t work with how gamescope functions.
The “official” method for installing steam is the debian package they provide on the website or using SteamOS on compatible hardware.
If we want gaming to succeed on Fedora, a Steam RPM (and it’s supporting dependencies) is necessary.