A good overview of the issue, from OSV News: 

As the Synod on Synodality opens Oct. 4 in Rome, among the most closely watched topics under discussion is the question of whether the Catholic Church can or will extend the permanent diaconate — restored after the Second Vatican Council — to women.

The synod’s working document released June 20 notes that most continental assemblies called for a discussion on the inclusion of women in the diaconate, and asked, “Is it possible to envisage this, and in what way?”

Up to now, the answer to that question is not clear and is debated.

“The key is not whether there were women deacons,” said Deacon Dominic Cerrato, director of the Office of the Diaconate in the Diocese of Joliet, Illinois, and editor of The Deacon magazine, published by OSV, which is also the parent company of OSV News…

… “Of course, there were women deacons. But tradition never called them part of the diaconate, never saw them as part of the diaconate,” he said.

The matter of women deacons or deaconesses, Deacon Cerrato maintained, has been “studied to death.”

In his understanding, the female diaconate role developed due to the ancient tradition of nude baptism — “it would not be appropriate for the bishop to see a woman in the nude,” he said — and to avoid potential scandal during individual catechetical instruction.

Deaconesses, said Deacon Cerrato, also examined signs of harm in spousal abuse cases.

“They emerged likely out of the order of widows and virgins,” he said, “and they probably morphed into abbesses and women religious.”

While Deacon Cerrato emphasized there is “no question of the historic place of deaconesses in the early church,” he cautioned — citing differences in ordination rites and discrepancies in liturgical, sacramental and ministerial roles — that this evidence is not enough to say their roles were equivalent to the male diaconate….

…Phyllis Zagano, adjunct professor of religion at Hofstra University on Long Island, and co-author of the 2012 book “Women Deacons: Past, Present, Future,” told OSV News that “if the church needs deacons, it stands to reason that it needs women deacons.”

Zagano served on the papal commission on women and the diaconate established in 2016, and previously remarked that the issue can be “partly resolved by the synod, then formally approved by the pope.”

“History notes that women were sacramentally ordained as deacons in various eras and various places,” Zagano told OSV News. “The liturgies used were examined in the 17th century by Jean Morin and found to meet the criteria for sacramental ordination according to the Council of Trent.”

As to the objection that opening the diaconate to women could be viewed as an encouragement to the priesthood, Zagano said, “Theologically, it is important to recognize that the diaconate is not part of the priesthood, and that diaconal ordination does not necessarily qualify anyone for priestly ordination.”

There’s much more. Read it all.