By default in WSL, certain characters used by particular applications (e.g. ⚠, the warning sign), show up as a question mark in a box. This is because the default font used, Consolas, does not support these characters.

In order to get them to display, you need to install a font that does. An oft-recommended one is “DejaVu Sans Mono for Powerline”, which can be found at the powerline fonts repository on GitHub.

Download all the .ttf files, then hit the Windows key and search for Font, then open Font Settings. Drag and drop the TTF files into the given box. You may experience some lag, but they should all show up correctly.

After this, right-click on the WSL title bar, select Properties, and open the Fonts tab. Scroll down the Font options until you see “DejaVuSans Mono for Powerline”, then select it.

After closing and re-opening WSL, these characters should appear correctly. If some still don’t, you’ll have to find a font that supports them.