Ran into this today, attaching the information requested in #51.

Unable to commission/install 18.04 with "No minimum kernel"

MAAS version: maas 2.5.3-7533-g65952b418-0ubuntu1~18.04.1 all

Guests kernel paniced on two hosts (host1 and host2), dpkg -l attached for each host.
Console output from each failed guest (vm*_console.log)
Libvirt xml from each failed guest (vm*.xml)
attaching squashfs, boot-kernel, and boot-initrd used by MAAS for the failed boots.

Running host kernels:
host1: Linux host1 5.0.0-17-generic #18~18.04.1-Ubuntu SMP Wed Jun 5 12:43:23 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
host2: Linux host2 4.15.0-52-generic #56-Ubuntu SMP Tue Jun 4 22:49:08 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

regiond log of latest image download:
2019-06-22 23:14:06 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/streams/v1/maas:v2:download.json HTTP/1.1 --> 200 OK (referrer: -; 
agent: python-simplestreams/0.1)
2019-06-22 23:14:09 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/ga-18.04-lowlatency/bionic/20190621/boot-initrd HTTP/1
.1 --> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:09 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/ga-18.04-lowlatency/bionic/20190621/boot-kernel HTTP/1
.1 --> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:19 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/ga-18.04-lowlatency/bionic/20190621/squashfs HTTP/1.1 
--> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:22 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/ga-18.04/bionic/20190621/boot-initrd HTTP/1.1 --> 200 
OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:23 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/ga-18.04/bionic/20190621/boot-kernel HTTP/1.1 --> 200 
OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:27 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/hwe-18.04-edge/bionic/20190621/boot-initrd HTTP/1.1 --
> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:27 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/hwe-18.04-edge/bionic/20190621/boot-kernel HTTP/1.1 --
> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:30 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/hwe-18.04-lowlatency-edge/bionic/20190621/boot-initrd 
HTTP/1.1 --> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:31 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/hwe-18.04-lowlatency-edge/bionic/20190621/boot-kernel 
HTTP/1.1 --> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:31 regiond: [info] 127.0.0.1 GET /MAAS/rpc/ HTTP/1.1 --> 200 OK (referrer: -; agent: provisioningserver.rpc.clusterservi
ce.ClusterClientService)
2019-06-22 23:14:35 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/hwe-18.04-lowlatency/bionic/20190621/boot-initrd HTTP/
1.1 --> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:35 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/hwe-18.04-lowlatency/bionic/20190621/boot-kernel HTTP/
1.1 --> 200 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:39 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/hwe-18.04/bionic/20190621/boot-initrd HTTP/1.1 --> 200
 OK (referrer: -; agent: python-simplestreams/0.1)
2019-06-22 23:14:39 regiond: [info] 127.0.0.1 GET /MAAS/images-stream/ubuntu/amd64/hwe-18.04/bionic/20190621/boot-kernel HTTP/1.1 --> 200 OK (referrer: -; agent: python-simplestreams/0.1)