I convert schedules directly from the newspapers into OOTP format. I don't know if there is an interim step where you transfer that raw data into a different format and then into OOTP format.
Le Grand Orange (LGO) had a bunch of minor-league schedules that he put into his own format and then Outlaw Jim converted those into OOTP schedules. How he did it, though, I have no idea, and Outlaw Jim hasn't been around these boards since April 2020. His schedules are in this thread if you want to see them.
I trust that doesn't answer your question
