root@test-focal:~# apt policy ubuntu-advantage-tools
ubuntu-advantage-tools:
  Installed: 27.13.1~20.04.1
  Candidate: 27.13.1~20.04.1
  Version table:
 *** 27.13.1~20.04.1 500
        500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     20.3 500
        500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
root@test-focal:~# apt policy update-notifier-common
update-notifier-common:
  Installed: 3.192.30.14
  Candidate: 3.192.30.14
  Version table:
 *** 3.192.30.14 500
        500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     3.192.30 500
        500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
root@test-focal:~# /usr/lib/update-notifier/apt-check --human-readable
0 updates can be applied immediately.
root@test-focal:~# echo "deb http://archive.ubuntu.com/ubuntu focal-proposed main" | tee /etc/apt/sources.list.d/proposed.list
deb http://archive.ubuntu.com/ubuntu focal-proposed main
root@test-focal:~# apt update
Get:1 http://security.ubuntu.com/ubuntu focal-security InRelease [114 kB]
Hit:2 http://archive.ubuntu.com/ubuntu focal InRelease   
Get:3 http://archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
Get:4 http://archive.ubuntu.com/ubuntu focal-backports InRelease [108 kB]
Get:5 http://archive.ubuntu.com/ubuntu focal-proposed InRelease [267 kB]
Get:6 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages [2340 kB]
Get:7 http://archive.ubuntu.com/ubuntu focal-updates/universe amd64 Packages [1019 kB]
Get:8 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 Packages [232 kB]
Get:9 http://archive.ubuntu.com/ubuntu focal-proposed/main Translation-en [50.8 kB]
Get:10 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 c-n-f Metadata [1424 B]
Fetched 4247 kB in 4s (1077 kB/s)                                
Reading package lists... Done
Building dependency tree       
Reading state information... Done
29 packages can be upgraded. Run 'apt list --upgradable' to see them.
root@test-focal:~# apt install update-notifier-common
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'apt autoremove' to remove it.
The following packages will be upgraded:
  update-notifier-common
1 upgraded, 0 newly installed, 0 to remove and 28 not upgraded.
Need to get 173 kB of archives.
After this operation, 2048 B disk space will be freed.
Get:1 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 update-notifier-common all 3.192.30.16 [173 kB]
Fetched 173 kB in 1s (133 kB/s)                  
(Reading database ... 41494 files and directories currently installed.)
Preparing to unpack .../update-notifier-common_3.192.30.16_all.deb ...
Unpacking update-notifier-common (3.192.30.16) over (3.192.30.14) ...
Setting up update-notifier-common (3.192.30.16) ...
root@test-focal:~# apt policy update-notifier-common
update-notifier-common:
  Installed: 3.192.30.16
  Candidate: 3.192.30.16
  Version table:
 *** 3.192.30.16 500
        500 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     3.192.30.14 500
        500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
     3.192.30 500
        500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
root@test-focal:~# /usr/lib/update-notifier/apt-check --human-readable
Expanded Security Maintenance for Applications is not enabled.

28 updates can be applied immediately.
To see these additional updates run: apt list --upgradable

1 additional security update can be applied with ESM Apps.
Learn more about enabling ESM Apps service at https://ubuntu.com/esm
root@test-focal:~#