Check Nexx Smart Alarm Compatibility by Panel Image
This is a partial list. Many supported panels were sold under different names and model numbers so here are some tips for seeing if your panel will be compatible.
Look for a large wiring sticker inside the panel enclosure that shows the word(s): Vista, Ademco, Honeywell, etc.
Look on the panel for words like SAVS and a series of letters and numbers like SAVS20P5 or SAVS10SECE. The model number is embedded inside this string of characters as demonstrated here.