Do Qolsys panels work with extended antennas or cell booster kits?

No. It is not possible to add an extended antenna or cell booster kit to Qolsys panels. 

Qolsys panels use an antenna that is built into the panel. The connection between the panel and the built-in antenna is not an MMCX connection, which the Alarm.com extended antennas and cell booster kits use. Due to the method used to connect the panel to the antenna, it is not possible to disconnect the panel from the antenna to extend it without damaging the panel.

To improve signal strength, place the panel in an area that receives the best signal at the location.