True, some modules are under the GPL only. Here[0] is a very nice website showing an overview.
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...