You can use this app template:
https://marketplace.qt.io/products/qt-lgpl-app-template
Offers you a relink mechanism, also for embedded devices:
you can release a redistributable project (your application inside a compiled static library, in a qt .pro project)
and you must release your SDK (sysroot and compiler).
If you use Static Qt, user can build his own Qt and rebuild your closed source application.

Why would it be ? You don't need to own a big company to be a customer. AFAIK, you fit in the target audience of the Indie Mobile License