Here is from Lakewood Bays Havaad, covering some of the sources we talked about here:
Question: We have stated that one should avoid taking tzedakah if he has the option of supporting himself. Today, there are thousands of people learning in Kollel. Many of them are supported by the public’s generosity. Since they technically could get a job and support themselves, is learning full-time a contradiction to the Gemara’s statement that one should avoid taking charity?
Answer: It is true that Chazal say it is preferable to take any job than to live off of tzedakah; however, the Rambam says that anyone who accepts to spend his days learning Torah should be supported by the public.
In olden times, Shevet Levi sat and learned all day and they were taken care of by the rest of the nation. The Rambam says that anyone who so desires can emulate Shevet Levi and accept to learn full-time while the public supports him.
These people are needed to sustain the world through their Torah studies, and, therefore, are an exception to the above-stated rule that one should do any kind of labor in order to avoid accepting charity. All Poskim agree that this is true and maintain that supporting such men is an ideal form of tzedakah.
The Chofetz Chaim speaks about this in many places and says that the best use of tzedakah funds is to support poor Torah scholars who wouldn’t be able to learn otherwise without your help. These funds directly contribute to the dissemination of Torah through the generations and are necessary to sustain the world.