I have said it once and I will say it again: You really should think twice about buying Qt embedded licenses. Unless you really need an embedded version of Qt the LGPL variant is probably fine for you.
Everyone who is saying that Qt is too expensive -> It's free. Just Use LGPL. All the tools are GPL but that doesn't matter if you don't want to link against those. The Libraries itself are LGPL so you can dynamically link against them with attribution.
Everyone who is saying that they need the Qt Support -> You probably don't. If you live on the bleeding edge you sometimes get cut. Qt for all its flaws really is fine. And if you get stuck the community will help out just as good.
Everyone who is saying that they already bought into it -> Bad news for you. The license terms of the commercial license are very restrictive. If you are building an application which communicates over a network or building a system which consists of multiple programs you have to make sure you don't integrate or communicate with a program which uses the LGPL variant[0]. Yes that's right, if you pay them money you better make sure that you never run your program on KDE because it would inadvertently communicate with software that you are not allowed to communicate with. Of course you are allowed to communicate with everyone while using the LGPL.
ALWAYS use the LGPL variant! Unless you are not able to work within the boundaries of it.
If you have to spend money you are better off donating to the KDE Free Qt Foundation.
[0]https://embeddeduse.com/2023/01/06/using-qt-5-15-and-qt-6-un...
I strongly agree with this, with one caveat: there are a few modules that are GPL and not LGPL. Definitely check the module licenses to make sure you're not going to need anything that is GPL. Most likely you won't.
On an unrelated note, as someone who mainly builds desktop tools and has used Qt for many many years, but would like to get away from C++ for UI logic, I can't see any reasonable alternative, but would love for some suggestions.
Qt just makes so many things easy, and basically every use-case is well-explored. Most other options seem to just focus on making easy things easy. As soon as you want to render something in 3D, make a node editor, call into or share data with C++ libraries, implement a reasonable undo/redo system, re-skin the UI to not look like a children's app, etc, other options fall flat.
As for alternatives there really is not much to choose from. For small projects which are not reliant on the performance/native designs of Qt, Dear ImGui looks nice[1]. But it is very much tailored for a different Use Case.
Edit: I said that [0] is a nice website. But you only get a complete view of the situation if you cycle through all of the open source licenses. Too bad there is no "Open Source" option. Would hurt their sales I guess...