pfSense

This is a static php page (not generated from XML) I believe, so the package maintainer needs to update it to be compatible with 2.3

You are correct.
I doubt that Cron has a "maintainer". I suspect that the packages like Cron, System Patches, Service Watchdog, ... are kind of "pfSense add-ons" developed in-house.
If no-one else looks at it I will have a go so I learn what is required, but time for bed for me now.

Phillip Davis wrote:

I guess the underlying package GUI generation code has not yet been updated to the font-awesome icons and still generates references to older icons that no longer exist? or?

There simple are direct references to the old themes icons. E.g., with cron:

https://github.com/pfsense/pfsense-packages/blob/master/config/cron/cron.php#L121

All of this porting would better be done in https://github.com/pfsense/FreeBSD-ports/tree/devel/sysutils/pfSense-pkg-Cron directly, instead of adding useless version-specific shit to current package code - but someone needs to stop syncing the code with the pfsense-packages repo once it's done.

This is better covered by https://redmine.pfsense.org/issues/5571
I have been away from much open-source stuff last week. Now catching up on what has happened. Probably best for me not to bother converting a package until there is a good example done by an ESF person. Then I can mindlessly copy the style and save a lot of back-and-forth in pull requests :)
I suggest close this issue.