I figured it out, it wasn't very clear in the documentation, but it looks like if you have a stack where at least one of the stack line items is based on a model column, you can make the stack sortable on that column like so:
Stack::make('Name & Description', 'name', [
Line::make('Name')
->asHeading(),
Line::make('Description', function () {
return Str::limit($this->description, 50);
})->asSmall(),
])->sortable()->onlyOnIndex(),
So the above is the name and description column, and it's sortable on the name column, which is exactly what I wanted.