Check that cron has been run recently - in the last 72 hours

Better status.

I didn't test or look at the code much.

One nitpick is that comments should end with a period.

As Drupal6 has been EOL https://www.drupal.org/about/drupal6-eol closing as outdated

This one also feels nice to keep in modern versions as cron is still important, I believe, for security.

Not sure what to check though. Each project runs cron at different intervals. Or if you use ultimate cron some cron jobs run at different times.

If the dblog module is enabled and if there are messages in the table about cron that seems like enough to me?

I guess a more robust solution is this module could have its own cron task that sets a variable to the last time it ran and then during review phase if that variable is too old it would alert that cron is not running?

what do we consider too old though? That could be different per site. 24hours?

For purposes of the module I think the really bad situation would be if cron hadn't run in a long time (days, weeks, etc.). Seems good to check it has run in the last ~72 hours?

If we use 24 and a site has cron running once a day then there's a risk if cron doesn't run for 1 day or is late that it would get flagged as a problem when that's not really a problem. It seems good to balance the security and not sending too many error messages.

Try this.

The quotes (double vs single) are a little inconsistent on the user-facing strings here:

+        return $this->t("Unexpected result.");

Otherwise LGTM!

Updated.

LGTM. Thanks.