When I last did a client project using Qt they were intentionally running an older open source version (3.x?) in order to avoid having to pay license fees.
Likewise, I wonder if this latest mix of licenses can be used without fees.
Most of Qt ships under your choice of 3 different licenses: GPL, Commercial, and LGPL. Their sales people and marketing material like to pretend the LGPL version doesn't exist, and that you need a Commercial license to do any commercial software development.
But that's just not the case. The LGPL license works great for many/most commercial applications.
(Watch out for a couple of the addons/extras that don't have an LGPL version.)
I thought the open source support window for Qt5 ended years ago.
Why are they still pushing updates if they could just sell highly priced commercial licenses for extended support? That is what I would expect of the Qt Company…
Worth noting that KDE maintains a patched open source Qt releases with additional patches that may only be in commercial releases https://invent.kde.org/qt/qt/qt5/
> Find them in the Qt Online Installer. It will steer you to the right download version and help you install tools and add-on components that are available for your open source license.
Edit: looks like it's a mix of GPLs, LGPLs, and their own license.
https://en.wikipedia.org/wiki/Qt_%28software