Unsolved Smart home system
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Short answer: yes.
Long answer: if your product will be distributed only within a closed group of people who you trust (i.e., you are 100% sure they won't be looking for ways to sue you or do other nasty things), you may disregard all conditions of free licenses used in Qt modules, and just do anything you like with it (including modifications in Qt itself or even borrowing parts of its code into your project)
However, if you are (eventually) planning to give your product away as a public download, or sell it, you need to read licenses and comply to their terms. IOW, you still don't have to pay anyone for using Qt, but there are some restrictions on how you distribute your product, how you make modifications to Qt's code, and which pieces you can or cannot borrow from Qt code.
FWIW, if you make your project open source under GPL license, and not planning to sell devices which runit as a part of firmware, you can also ignore all license stuff and be safe. But if you are planning to produce such devices, it's better to consult a lawyer, though it's still possible to do with open source Qt if users can reflash device or have read-write access to its file system and can build their own Qt for them.