You CAN do bulk operations in Gramps via import. That you can leverage features for bulk operations just isn’t terribly intuitive. (For those of us conditioned the old days of punch cards, leveraging features to re-use data sources is 2nd nature. You just have to be aware of the law of unintended consequences.)
For instance, outputting a client’s phone & eMail address books as vCards for import is an interesting ways to jumpstart creating their personal Tree.
As @SNoiraud, pointed out, a list of Sources (without relationship to events, Persons, etc cetera) is of limited utility. Personally, I think you’d be better off importing the directory into a document management system and first organize it there. You could then output a CSV sample from both the Document Management System & an example 1 person sourced Tree in Gramps (to facilitate reconfiguring the data) and import that into a blank Test Gramps Tree.
Several of the Gramplets also do mini bulk updates.