There are few that one can point to it being their opinion. Lactantius is the only one which claims it's a matter of faith. St. Basil and St. Augustine explicitly say this topic is not in Scripture and is not worthy of serious thought. No one's saying they were ignorant. The ones who did hold the FE opinion seemed to hold it not as a matter of faith, but as the common opinion where they were. Like I said though, there weren't that many who wrote about it.
The only reason it's debatable is because the FE's are trying to destroy all credibility of the Church, so they try to tie it into the Catholic Faith. They get Catholics to believe in it by exaggerating the importance among the Fathers and twisting Scripture to attempt to make it a religious matter. There's a reason why this subject was not brought up for about 1500 years.
Augustine says many things about the flat earth, including the quotes provided above about the firmament. The intended purpose of bringing flat earth up time and again is to get people to take seriously the subject and dig up docuмents for full evaluation, do experiments, study the subject with an open mind. There is a trend in the Church and it doesn't favor the globe pretty much ever. For those who insist on calling me and others "dogmatic flat earthers", your attempts to discourage discussion, thwart the words and intentions of the Fathers, and otherwise use categorical commentary to denounce people shows contempt for no reason.