Welcome to the SmartThings Community, @mbdrlp!
So, as I understand, you installed the Zigbee thermostat device in SmartThings using the handler you shared above (this means you copied the DTH and pasted it in your IDE)?
Or directly from the ST app (this means you entered the device catalog and followed the steps displayed)? If so, this is the handler used by the device as this was published by Sinopé
“outdoorTemp” is a custom attribute, which means it is not saved in the ST API, that’s why it is not shown in the mobile app either. To see it on both sides it should be converted to a custom capability and follow other migration steps explained in this post.
I don’t know how Jeedom integrates with SmartThings but not all third-party integrations recognize custom capabilities (especially those that still use the Groovy environment) so, you should verify that first.