In the past, we've been able to provision cm3 devices with 4GB emmc on with core images. However, when trying to use the core20 image from 20200527, it does not complete the install. I found this in the serial log:
Installing the system, please wait for reboot
-- Logs begin at Tue 2019-11-19 12:24:25 UTC. --
May 28 02:32:10 ubuntu systemd[1]: Starting Snap Daemon...
May 28 02:32:10 ubuntu snapd[1131]: AppArmor status: apparmor is enabled and all features are available
May 28 02:32:11 ubuntu snapd[1131]: daemon.go:343: started snapd/2.45+git27.ga58e708 (series 16) ubuntu-core/20 (armhf) linux/5.4.0-1011-raspi.
May 28 02:32:11 ubuntu snapd[1131]: daemon.go:436: adjusting startup timeout by 35s (pessimistic estimate of 30s plus 5s per snap)
May 28 02:32:11 ubuntu snapd[1131]: helpers.go:961: cannot retrieve info for snap "pi-kernel": cannot find installed snap "pi-kernel" at revision 156: missing file /snap/pi-kernel/156/meta/snap.yaml
May 28 02:32:11 ubuntu systemd[1]: Started Snap Daemon.
May 28 02:32:29 ubuntu snapd[1131]: secboot_tpm.go:36: checking if secure boot is enabled...
May 28 02:32:29 ubuntu snapd[1131]: secboot_tpm.go:38: secure boot not enabled: not a supported EFI system
May 28 02:32:29 ubuntu snapd[1131]: handlers_install.go:138: create and deploy partitions
May 28 02:32:30 ubuntu snapd[1131]: taskrunner.go:271: [change 2 "Setup system for run mode" task] failed: cannot create partitions: gadget and /dev/mmcblk0 partition table not compatible: device /dev/mmcblk0 (3.64 GiB) is too small to fit the requested layout (4.91 GiB)
This should be fixed now with the pi gadget in beta - thanks to Lukasz for this fix :)