texture viewer cannot dump certain textures

[tony56a]

For certain assets, I've noticed that I am unable to get a png dump of the texture due to this error:
Unsupported texture format - needs to be ARGB32, RGBA32, RGB24, Alpha8 or one of float formats

I suspect that the reason for this is probably because the texture's using DXT5, and that is somehow not readable with EncodeToPng or something (the Unity docs somewhat indicates that this is the case). If it's possible, can you first convert the texture into a readable format, like RGBA32, then do the dump?