Theophylact of Ohrid

When this estate has been squandered and a person lives neither according to reason, that is, according to natural law, nor follows the written Law, nor listens to the prophets, then a severe famine sets in (for him)—not a famine of bread, but a famine of hearing the word of the Lord (Amos 8:11). And he begins to "be in want," since he does not fear the Lord but stands far from Him, whereas for those who fear the Lord "there is no want" (Ps. 34:10). Why is there no want for those who fear the Lord? …

Commentary on Luke ↗

Augustine of Hippo

As it follows, And when he had spent all, there arose a great famine in that land. The famine is the want of the word of truth. It follows, And he began to be in want. Fitly did he begin to be in want who abandoned the treasures of the wisdom and the knowledge of God, and the unfathomableness of the heavenly riches.

Catena Aurea by Aquinas ↗

Bede

And when he had spent all, there arose a mighty famine in that country. All the things he wasted signify the adornments of nature which he consumed. The famine in the far country is the lack of the word of truth, in the forgetfulness of the Creator. Concerning which it is said in the prophets: Because the Lord will send a famine on the land, not a famine of bread, nor a thirst for water, but of hearing the words of the Lord (Amos 8).

On the Gospel of Luke ↗

Bonaventure

And after he had consumed all things, etc. After describing the insolence of the prodigal son, here he describes his misery and want, and this with respect to three things, namely with respect to the hardship of famine, with respect to the disgrace of servitude, and with respect to the most extreme kind of beggary. …

Commentary on Luke, Chapter 15 ↗