Kuga Hybrid Alarm System Fault

Sounds like a pain. Did you check the basic stuff like fuses and battery voltage? Sometimes a low voltage can cause weird errors with the alarm system.

Which specific fuses should I check, and what's the acceptable battery voltage for the alarm to work right?

Check the fuses related to the alarm system and central locking - usually in the fuse box under the dash or in the engine compartment. As for voltage, anything below 12V when the engine is off might be suspect. If the basics check out, you might need to visit a workshop.

A workshop visit was needed. It was a defective plug connection. The repair, including replacing the connector and checking the alarm, cost 95€. Thanks for the help.