@idefix37
I found the solution, thanks!
Thanks to your screenshot, I realized that the issue with the white map background after applying a custom color scale was caused by the color assigned to the zero value.
In my case, I had set 0 to a very light color close to white, which made the entire map background appear white.
I changed it to a dark gray instead, and now the map background looks just like the default again.
I just realized what you meant in the other topic 😂
Really appreciate your help