Comment 15 for bug 1959047

Bionic verification was successfully done using the steps outlined in the bug description. The important parts are captured here:

$ lxc exec lp1959047 -- apt-get install -y lxd
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  acl apparmor dns-root-data dnsmasq-base ebtables iptables libip6tc0 libiptc0 liblxc-common liblxc1 liblzo2-2 libnetfilter-conntrack3 libnfnetlink0 libuv1 lxcfs lxd-client rsync squashfs-tools uidmap xdelta3
Suggested packages:
  apparmor-profiles-extra apparmor-utils criu lxd-tools openssh-server
The following NEW packages will be installed:
  acl apparmor dns-root-data dnsmasq-base ebtables iptables libip6tc0 libiptc0 liblxc-common liblxc1 liblzo2-2 libnetfilter-conntrack3 libnfnetlink0 libuv1 lxcfs lxd lxd-client rsync squashfs-tools uidmap xdelta3
0 upgraded, 21 newly installed, 0 to remove and 9 not upgraded.
Need to get 10.9 MB of archives.
After this operation, 41.3 MB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu bionic/main amd64 libnfnetlink0 amd64 1.0.1-3 [13.3 kB]
Get:2 http://archive.ubuntu.com/ubuntu bionic/main amd64 liblzo2-2 amd64 2.08-1.2 [48.7 kB]
Get:3 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 apparmor amd64 2.12-4ubuntu5.1 [487 kB]
Get:4 http://archive.ubuntu.com/ubuntu bionic/main amd64 libip6tc0 amd64 1.6.1-2ubuntu2 [19.9 kB]
Get:5 http://archive.ubuntu.com/ubuntu bionic/main amd64 libiptc0 amd64 1.6.1-2ubuntu2 [9308 B]
Get:6 http://archive.ubuntu.com/ubuntu bionic/main amd64 libnetfilter-conntrack3 amd64 1.0.6-2 [37.8 kB]
Get:7 http://archive.ubuntu.com/ubuntu bionic/main amd64 iptables amd64 1.6.1-2ubuntu2 [269 kB]
Get:8 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 rsync amd64 3.1.2-2.1ubuntu1.3 [335 kB]
Get:9 http://archive.ubuntu.com/ubuntu bionic/main amd64 acl amd64 2.2.52-3build1 [38.5 kB]
Get:10 http://archive.ubuntu.com/ubuntu bionic/main amd64 dns-root-data all 2018013001 [5360 B]
Get:11 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 dnsmasq-base amd64 2.79-1ubuntu0.5 [307 kB]
Get:12 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 ebtables amd64 2.0.10.4-3.5ubuntu2.18.04.3 [79.9 kB]
Get:13 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 liblxc1 amd64 3.0.3-0ubuntu1~18.04.1 [264 kB]
Get:14 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 liblxc-common amd64 3.0.3-0ubuntu1~18.04.1 [438 kB]
Get:15 http://archive.ubuntu.com/ubuntu bionic/main amd64 libuv1 amd64 1.18.0-3 [64.4 kB]
Get:16 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 lxcfs amd64 3.0.3-0ubuntu1~18.04.2 [39.0 kB]
Get:17 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 lxd-client amd64 3.0.3-0ubuntu1~18.04.2 [3025 kB]
Get:18 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 squashfs-tools amd64 1:4.3-6ubuntu0.18.04.4 [111 kB]
Get:19 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 uidmap amd64 1:4.5-1ubuntu2.3 [68.0 kB]
Get:20 http://archive.ubuntu.com/ubuntu bionic/main amd64 xdelta3 amd64 3.0.11-dfsg-1ubuntu1 [68.9 kB]
Get:21 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 lxd amd64 3.0.3-0ubuntu1~18.04.2 [5199 kB]
Fetched 10.9 MB in 4s (2980 kB/s)
...
Unpacking xdelta3 (3.0.11-dfsg-1ubuntu1) ...
Selecting previously unselected package lxd.
Preparing to unpack .../20-lxd_3.0.3-0ubuntu1~18.04.2_amd64.deb ...
Adding system user `lxd' (UID 105) ...
Adding new user `lxd' (UID 105) with group `nogroup' ...
Creating home directory `/var/lib/lxd/' ...
Adding group `lxd' (GID 109) ...
Done.
Unpacking lxd (3.0.3-0ubuntu1~18.04.2) ...
...
Setting up liblxc1 (3.0.3-0ubuntu1~18.04.1) ...
Setting up liblxc-common (3.0.3-0ubuntu1~18.04.1) ...
apparmor.service is not active, cannot reload.
invoke-rc.d: initscript apparmor, action "reload" failed.
Setting up lxd (3.0.3-0ubuntu1~18.04.2) ...
...

$ lxc exec lp1959047 -- lxc exec c1 -- journalctl -b0 --grep 'Failed to set up namespace'
-- No entries --

So it worked, thanks!