Hitting the same issue with Dell Precision device and the latest 19.04 RC image (0416).

Abstract from the syslog (attached):

Apr 17 10:14:44 ubuntu ubiquity: Reading package lists...
Apr 17 10:14:44 ubuntu ubiquity: 
Apr 17 10:14:44 ubuntu ubiquity: Building dependency tree...
Apr 17 10:14:44 ubuntu ubiquity: 
Apr 17 10:14:44 ubuntu ubiquity: Reading state information...
Apr 17 10:14:44 ubuntu ubiquity: 
Apr 17 10:14:44 ubuntu ubiquity: The following additional packages will be installed:
Apr 17 10:14:44 ubuntu ubiquity:   dkms libnvidia-cfg1-418 libnvidia-common-418 libnvidia-compute-418
Apr 17 10:14:44 ubuntu ubiquity:   libnvidia-decode-418 libnvidia-encode-418 libnvidia-fbc1-418
Apr 17 10:14:44 ubuntu ubiquity:   libnvidia-gl-418 libnvidia-ifr1-418 libvdpau1 libxnvctrl0 mesa-vdpau-drivers
Apr 17 10:14:44 ubuntu ubiquity:   nvidia-compute-utils-418 nvidia-dkms-418 nvidia-kernel-common-418
Apr 17 10:14:44 ubuntu ubiquity:   nvidia-kernel-source-418 nvidia-prime nvidia-settings nvidia-utils-418
Apr 17 10:14:44 ubuntu ubiquity:   pkg-config screen-resolution-extra vdpau-driver-all
Apr 17 10:14:44 ubuntu ubiquity:   xserver-xorg-video-nvidia-418
Apr 17 10:14:44 ubuntu ubiquity: Suggested packages:
Apr 17 10:14:44 ubuntu ubiquity:   menu libvdpau-va-gl1 nvidia-vdpau-driver nvidia-legacy-340xx-vdpau-driver
Apr 17 10:14:44 ubuntu ubiquity:   nvidia-legacy-304xx-vdpau-driver
Apr 17 10:14:44 ubuntu ubiquity: Recommended packages:
Apr 17 10:14:44 ubuntu ubiquity:   libnvidia-compute-418:i386 libnvidia-decode-418:i386
Apr 17 10:14:44 ubuntu ubiquity:   libnvidia-encode-418:i386 libnvidia-ifr1-418:i386 libnvidia-fbc1-418:i386
Apr 17 10:14:44 ubuntu ubiquity:   libnvidia-gl-418:i386
Apr 17 10:14:44 ubuntu ubiquity: The following NEW packages will be installed:
Apr 17 10:14:44 ubuntu ubiquity:   dkms libnvidia-cfg1-418 libnvidia-common-418 libnvidia-compute-418
Apr 17 10:14:44 ubuntu ubiquity:   libnvidia-decode-418 libnvidia-encode-418 libnvidia-fbc1-418
Apr 17 10:14:44 ubuntu ubiquity:   libnvidia-gl-418 libnvidia-ifr1-418 libvdpau1 libxnvctrl0 mesa-vdpau-drivers
Apr 17 10:14:44 ubuntu ubiquity:   nvidia-compute-utils-418 nvidia-dkms-418 nvidia-driver-418
Apr 17 10:14:44 ubuntu ubiquity:   nvidia-kernel-common-418 nvidia-kernel-source-418 nvidia-prime
Apr 17 10:14:44 ubuntu ubiquity:   nvidia-settings nvidia-utils-418 pkg-config screen-resolution-extra
Apr 17 10:14:44 ubuntu ubiquity:   vdpau-driver-all xserver-xorg-video-nvidia-418
Apr 17 10:14:44 ubuntu ubiquity: 0 upgraded, 24 newly installed, 0 to remove and 0 not upgraded.
Apr 17 10:14:44 ubuntu ubiquity: Need to get 69.6 MB/69.7 MB of archives.
Apr 17 10:14:44 ubuntu ubiquity: After this operation, 344 MB of additional disk space will be used.
(...)
Apr 17 10:21:02 ubuntu ubiquity: Generating a new Secure Boot signing key:
Apr 17 10:21:02 ubuntu ubiquity: Can't load /var/lib/shim-signed/mok/.rnd into RNG
Apr 17 10:21:02 ubuntu ubiquity: 140099807978624:error:2406F079:random number generator:RAND_load_file:Cannot open file:../crypto/rand/randfile.c:98:Filename=/var/lib/shim-signed/mok/.rnd
Apr 17 10:21:02 ubuntu ubiquity: Generating a RSA private key
Apr 17 10:21:02 ubuntu ubiquity: .
Apr 17 10:21:02 ubuntu ubiquity: message repeated 10 times: [ .]
Apr 17 10:21:02 ubuntu ubiquity: +
Apr 17 10:21:02 ubuntu ubiquity: message repeated 4 times: [ +]
Apr 17 10:21:02 ubuntu ubiquity: .
Apr 17 10:21:02 ubuntu ubiquity: message repeated 22 times: [ .]
Apr 17 10:21:02 ubuntu ubiquity: +
Apr 17 10:21:02 ubuntu ubiquity: message repeated 4 times: [ +]
Apr 17 10:21:02 ubuntu ubiquity: writing new private key to '/var/lib/shim-signed/mok/MOK.priv'
Apr 17 10:21:02 ubuntu ubiquity: -----
Apr 17 10:21:02 ubuntu ubiquity[3176]: debconffilter_done: ubi-prepare (current: ubi-prepare)

So it takes around 6 minutes on this very beefy laptop to download, install and configure the drivers, during which the user doesn't know what's going on (unless he goes lurking in /var/log/syslog like I did :))