Pre-built library now built with 1.3.14 of paho.mqtt.c - fixes fo 1.3.12 listed here.
The pre-build Linux library from Paho MQTT (https://github.com/eclipse-paho/paho.mqtt.c/releases/tag/v1.3.14) is built with the latest version of Ubuntu, so may cause issues when running on older systems (e.g. RedHat9/etc). Details of building from source are detailed here https://github.com/KxSystems/mqtt/blob/master/docs/install.md#installing-a-release , which will prevent that issue from occurring.
Example Dockerfiles included now build with 1.3.14
When using Paho MQTT 1.3.14 with a proxy, the operation has changed to require use of a environment variable setting PAHO_C_CLIENT_USE_HTTP_PROXY , as detailed here: https://github.com/KxSystems/mqtt/blob/master/docs/reference.md#proxy-options