Having installed the Arduino IDE using the instructions on the offical Arduino site (mostly) I came across and issues with the UI when running under DWM a tiling window manager. The interface was squeezed down with menus opening in the middle of the screen and new windows such as the board manager opening an empty grey box as shown in the image below.

The Arch Wiki describes this situation and potential fixes. The fix that worked for me in this instance was along the lines of the first suggested fix in the wiki. By setting the environment variable and then running the IDE this issue is resolved. For my use case I do this in a script I run to launch the IDE which contains the following lines:

export _JAVA_AWT_WM_NONREPARENTING=1
/opt/arduino/arduino

Re-launching the UI now displays as expected as shown below.