Unlike flatpak, KDE Discover and GNOME Software do -not- work with snaps on Nobara.
You can instead install Snap Store from the Nobara Welcome App --> Recommended Additions.
If using terminal, the snap-store should be automatically installed when snapd is installed (sudo dnf in snapd), or using:
sudo snap install snap-store
If you get errors on installing snap-store (now renamed to "App Center") for newly installed snap, you might need some preparations.
As snap warnings may tell you, you need to enable snapd AppArmor service for snap apps to run:
systemctl enable --now snapd.apparmor
For error like error: too early for operation, device not yet seeded or device model not acknowledged, check:
systemctl status snapd.seeded.service
Reset it, if it's inactive (dead):
sudo systemctl restart snapd.seeded.service
Finally, snap might complain about snap-store that error: cannot install "snap-store": experimental feature disabled. This can be fixed by:
sudo snap set system experimental.user-daemons=true