I haven’t seen any official images for Fedora or Debian yet. I think that they are waiting for a few more things to get upstream so that their regular builds will work. For distros that do have images, like Ubuntu and OpenSuse, I think that they are building stuff by hand which is expensive and time consuming.
But with a little work you can build your own Fedora or Debian system by taking an existing system (like freedom-u-sdk) and then overwriting the rootfs with the Fedora/Debian rootfs. Then you just need a RISC-V rootfs which are available for Fedora and Debian.
These are Debian unleashed instructions, but unmatched is similar, just make sure to get the right parition number which is 4 now, and you should probably use nvme instead of sdcard.
I don’t know if you can get a Fedora rootfs directly. You might have to download an unleashed or qemu image, and then copy the rootfs from that overtop a freedom-u-sdk unmatched image rootfs.