simple64-gui is written in Qt6.
You can try this out by downloading simple64.
It is free/libre software under license GPLv3.0. Enjoy and happy hacking!
git clone https://github.com/simple64/simple64-gui.git
cd simple64-gui
mkdir build
cd build
cmake -G Ninja -DCMAKE_BUILD_TYPE=Release ..
VERBOSE=1 cmake --build .
Then you can run ./simple64-gui
.