Thanks for the help.
Adding #expanded in the Entrer button link was not really effective as it trigger expanded mode also for large screen and I don’t want that. I think I will go with the splash page. Even if it add an extra step for viewing the gallery on smartphone.
And it drives me to another point I can’t figure : when the splash page is active, the Thumb and Nav buttons are not aligned on the top right of the gallery when viewing on smartphone. Now if I disable the splash page, viewing the gallery on smartphone with #expanded and the buttons are perfectly aligned.
#expanded without splash page activate
#expanded with splash page activate
Do you have any ideas ?