People bring up this misconception every time Qt is mentioned. It is free as in beer (LGPL) at least on desktop. You can sell a proprietary commercial application using Qt without paying a dime as long as you dynamically link Qt (which can be included in the installation bundle).

(But you shouldn't. There is little need to distribute closed source software anymore. If you are shipping a binary with valuable trade secrets, then it won't be secret for very long. You can do server-side rendering of all the UI like all the large cap tech companies do then it won't matter if the client application at the edge is open source.)