You’re absolutely right, fc29 package is a culprit.
F30 has two versions of grubby: old one (we don’t need) in the package grubby-deprecated, and new one which we need in package grubby (but f30 version!).
So we’ll delete the f29 version:
sudo dnf remove grubby-8.40-18.fc29.x68_64
verify you now have just one installed:
sudo dnf list installed 'grubby*'
and I’d reinstall it just to be on a safe side:
sudo dnf reinstall grubby
After this check again, what grubby has to say:
sudo grubby --info ALL
It should list several boot options for f30 kernels.