It's not listed on the "Packages Manager" and when I try adding it manually from zip file downloaded from the I-CUBE-LRWAN website (version 1.2.1) I get an error saying "This Package version is not managed on this version of of STM32CubeMX".

I opened a support ticket with ST back in October (2018) highlighting a bug in their driver code that adds +1 dBm to a user's TX power request. If a 14 dBm TX power (EU limit in most 868 LoRa bands) is set by the user through the I-CUBE-LRWAN driver ...