Form-rows in inline layout incorrect

[DeD1rk]

Since django/django#16678, (I narrowed the main cause down to removal of float: left on fieldset .fieldBox here), form rows are not being rendered side-by-side.

Here is the relevant part of my code:

class ReportColumnInline(
    nested_admin.SortableHiddenMixin, nested_admin.NestedStackedPolymorphicInline
):
    class JSONResultColumnInline(
        nested_admin.SortableHiddenMixin, nested_admin.NestedStackedPolymorphicInline.Child
    ):
        model = JSONResultColumn


        fields = (("name", "result_type", "path"),)
    ...

Which shows up underneath each other, instead of inline:

If I find some more time I might add some more precise reproduction steps.