Oh it’s very popular in the automotive industry, especially for the in vehicle infotainment like navigation, radio, media playerand so on. They even offer a automotive specific version of it:
https://www.qt.io/industry/qt-in-automotive
Sadly most of the OEMs slowly move to Android.
I just bought a random UPS at MediaMarkt back in the day in Poland and calculated that it would be able to power all the CCTV cams, the CCTV recorder, a raspberry pi and the modem which is connected to a long range WiFi antenna for at least half an hour. This worked very well for a couple of years until the battery gave up. The one I had had a ethernet port but I never bothered to set it up to send the signal.
Mine was running at my parents summer house in Poland while my parents live in Germany and I in Sweden and now in Korea, so if something breaks down it’s down for up to a year until someone goes there to fix it.
Right now everything is down, my dad was there a couple of month ago and said that a marten chew up the Ethernet cables. Sadly my dad couldn’t fix it so now I hope I will be able to get there during Christmas.