Coming from https://github.com/FedoraQt/MediaWriter/issues/237#issuecomment-622082586 there is a problem with the releases JSON.
It seems to contain only one Silverblue image that is aarch64, i.e. ARM. This is not good, because then only that ARM image shows up in Fedora Image Writer. (see linked issue)
Thus, the JSON seems to be missing many architectures.
The JSON as of now seems to contain Silverblue images for both x86_64 and aarch64. This should be enough for the issue#237 from Fedora Media Writer.
to comment on this ticket.