In eazyBI you can import any select list field as dimension and any custom numeric field as a measure. See more details here https://docs.eazybi.com/eazybijira/data-import/custom-fields.
Then, when using the custom dimension on rows, you can see any measures - custom or standard - grouped by what value from the select list the issues have. See below example with custom select field T-shirt size and ‘just a number’ custom field - for issues that do not have the T-shirt size specified, the number field total shows under (none) T-shirt size while it is totaled for the other T-shirt sizes for issues that have it defined.
Let me know if I missed something and you have some further questions!
Lauma / firstname.lastname@example.org