My main use case for Debian is primarily server-side and IoT, or Internet of Things devices. I work with small devices like a Raspberry or an ESP32 for small local software solutions or small hardware devices.
One specific example of how I use Debian on those devices is a Wi-Fi captive portal. When a customer enters the public Wi-Fi, they receive a Wi-Fi captive portal, which enables them to log in and use the company Wi-Fi while being registered and monitored. This includes some web application services and IPtables, which is the firewall, providing a secure environment for customers to access the company's Wi-Fi network.
Regarding my main use case with Debian, I also have website applications on the server side that are on the internal domain. For example, I have a building that is part of the company, and I want to monitor IP cameras or security features detecting motion, checking the temperature, and ensuring the fire alarm is working.