Hi, all 
I add nvidia repo to system (/etc/yum.repos.d/rpmfusion-nvidia-driver.repo):
[rpmfusion-nvidia-driver]
name=RPMFusion nVidia Driver
baseurl=https://download1.rpmfusion.org/nonfree/fedora/nvidia-driver/$releasever/$basearch/
gpgcheck=0
enabled=1
Next, install it:
rpm-ostree install xorg-x11-drv-nvidia akmod-nvidia
Reboot and check (rpm-ostree status):
ostree://fedora:fedora/30/x86_64/silverblue
Version: 30.20190427.n.0 (2019-04-27T08:57:18Z)
BaseCommit: a602958b1097d0790361a8b907f6f6ecbb62b7bbf826b086401eafb4ffcb845d
GPGSignature: Valid signature by F1D8EC98F241AAF20DF69420EF3C111FCFC659B9
LayeredPackages: akmod-nvidia gnome-tweaks xorg-x11-drv-nvidia
Now the most interesting:
lspci -k | grep nou
Kernel driver in use: nouveau
Kernel modules: nouveau, nvidia_drm, nvidia
I tried blocking nouveau driver, but it didn’t help:
I add rd.driver.blacklist=nouveau to grub config and run grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
Maybe somebody is working fine?