Editor E8 has an option to exclude the PNG files for faster upload.

Option to include or exclude PNG textures when exporting for upload
- Exclude PNG to reduce file size and allow a faster upload
- This does not affect the appearance of a mod in game
- The PNG textures are not required for a functioning mod
- DDS (in-game textures) are included whichever option you choose
- PNG files can be useful if you allow derivatives of your mod

https://www.lfs.net/forum/thread/106792