Hi. I suggest you check this: Unreal Editor 5.7 UI interaction is broken on Linux for ~3 month already
Unfortunately is not fixed till today. There’s a bug report at the bottom of the thread so I hope 5.8 will bring some fixes.
Also, a developer tried to fix it, but they mentioned it would require a more complex solution than just patching the X11 version. That was back in January, and we haven’t heard anything from them since."