Ah, there’s a new padding option specifically for mobile which is set to 30px by default.
Go to “Customize > Layout > Container”.
However, it only allows you to set one value for all 4 sides of the content area.
If you only want 0px on top while keeping 30px on the other sides, you can use this CSS:
@media (max-width: 768px) {
@media (max-width: 768px)
.separate-containers .inside-article,
.separate-containers .comments-area,
.separate-containers .page-header,
.separate-containers .paging-navigation,
.one-container .site-content {
padding-top: 0px;
}
}