My understanding is that the Qt 6 build system is vastly easier to work with.

Also, Audacity is not the first major FOSS project to successfully migrate from wxWidgets to Qt: Dolphin, the GameCube/Wii emulator, made a similar migration several years ago[0][1][2][3].

[0]: https://dolphin-emu.org/blog/2017/06/03/dolphin-progress-rep...

[1]: https://dolphin-emu.org/blog/2018/02/03/dolphin-progress-rep...

[2]: https://dolphin-emu.org/blog/2018/05/02/legend-dolphin-lens-...

[3]: https://dolphin-emu.org/blog/2018/07/06/dolphin-progress-rep...