Mattermost [still won't alert admins][0] properly to security patch releases, and does not care whether you prefer the stability of ESR versions. It tells admins that fully patched and supported systems are a Problem, in bold red type on the Workspace Optimisation page of the System Console.
Here are a couple of scripts to run with cron, which actively alert you to updates. The shell script is simpler and assumes you want to be on the very latest version, or latest ESR version. The Python version lists all available updates and whether your major + minor version is currently supported.
Call one with env vars like so: