That is actually been done that way (plugged into the Diffuse_Color channel and its value set to zero) - it's only happening to one person... the rest of the people using this mat filedon't appear to be having any trouble seeing the texture in preview.

What I might try is do the Add node trick BB showed me some time ago: instead of setting Diffuse_Value to zero, set it to 1 and plug an Add node - with Value_1 and Value_2 both set to zero - into that channel.

Thanks for your replies, guys...

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks