We sort the report by Brand -- which is a picklist field, but the order is not working properly, I expect it should sort by alphabetically, the same order result we will see in Classic.
Try to convert the report to a summary or matrix report:
What is the cause?
The order of groupings containing Picklist field values is based on how the values are arranged in the picklist field itself, not the arrangement selected in the Sort Order.
The easy fix is by change the picklist value for that field, see this article Sort Picklists, if you need guidance on how to change picklist value.
However, if you don't have admin access, or for some reason, you are not allowed to change the order, you can add bucket field in the report, make sure to create the buckets in the order that you want the picklist values to be displayed on the report.
So, instead of using the original field, use this bucket field in the report.
Here an idea to vote to sort picklist values alphabetically, currently only have 470 points after 9 years.