Hello guys, Is there anyway to save .tga without alpha?
Thanks for your help !

Not at this point. There are some checks in the code to see whether the image has an alpha channel, but that's wrong, it should check if there are any (semi-) transparent pixels. So that would actually be a bug. The commit that added the plugin in 2014 also mentions:

"Move the tga loading code to its own plugin

This is a copy of the tga kimgio plugin from kdelibs. It needs
expanding to support more options for saving.
"