Finding out if an Ubuntu release is still supported on the command line?

Running ubuntu-support-status will tell you how long support lasts of everything you have installed, here's the output of mine as an example:

Support status summary of 'ivory':

You have 1904 packages (75.7%) supported until April 2021 (5y)
You have 14 packages (0.6%) supported until January 2022 (5y)
You have 83 packages (3.3%) supported until April 2019 (3y)
You have 237 packages (9.4%) supported until January 2017 (9m)

You have 80 packages (3.2%) that can not/no-longer be downloaded
You have 197 packages (7.8%) that are unsupported

Run with --show-unsupported, --show-supported or --show-all to see more details

Run hwe-support-status to get a simple result. Use --verbose option, otherwise user will see nothing if the system is not using LTS Enablement Stack.

Example result in 14.04 release with existing kernel:

$ hwe-support-status
$ hwe-support-status --verbose
You are not running a system with a Hardware Enablement Stack. \
Your system is supported until April 2019.

The above command is provided by update-manager-core package on Ubuntu, which is the same package that provides ubuntu-support-status command.

$ dpkg --search support-status
update-manager-core: /usr/bin/hwe-support-status
update-manager-core: /usr/bin/ubuntu-support-status

End users will just need this command: hwe-support-status --verbose