the command sudo dnf install steam gives me the following error
Last metadata expiration check: 0:00:50 ago on Fri Aug 25 19:25:40 2023.
allow_vendor_change is disabled. This option is currently not supported for downgrade and distro-sync commands
No match for argument: steam
Error: Unable to find a match: steam
Steam would be installed with that command from the rpmfusion-nonfree-steam repo which should be enabled through the gnome software panel. Did you enable the third-party repos with gnome software before attempting to install steam?
You can make a quick check to see what repos are enabled with the command dnf repolist which should show all currently enabled repos.
There is no steam package for aarch64, which is the architecture that Apple Silicon Macs running Asahi run, so you won’t be able to install it even if you enable rpmfusion-nonfree. At the present time, Steam isn’t supported on this platform. There’s ongoing work to make it available (via emulation, unless Valve decides to release an aarch64 build of it) down the road, but nothing in usable form just yet.