ah you're right!

the problem Im facing is that Im holding a legendary weapon when opening chest, and those have a fixed morph skin.
no wonder I always get the bone skin with the Gusket Musket...
too bad, the default hero weapon is always weaker in damage term

oh well, at least learned something new

As I mentioned in the guide, save before opening the chest, this method worked for me.

there is an old trick but ppl have only tried it on console..

First, you save the game before going to Road to Rule.
Then go in Road to Rule and open the chest weapon to morph it.
If its not the morph you want, just exit the game immediately (without leaving Road to Rule, since it'll autosave your progress).
The way to exit the game in console is bringing up dashboard and simply close the game so to speak.
Then reboot the game and load your last save and repeat

I wonder if it can work on PC as well...

is there any 'trick' to get the weapon morph you want?
Im trying to get the Auroran skin on Rifle, but I always get the Bone skin instead..

Cant exactly 'not' defeat many Hollow Men if you want to complete the Brightwall Academy Trial, but I've taken care not to get defeated at combat at all until opening chest to morph weapon.
Plus, I've tried to open as many chest as available before opening chest to morph..
Still got the Bone skin :(

You uploaded animated images! What a resource! Thank you Primo!