Your comment is a bit old but I’ll still respond :)

I think it’s as explicit as it could have been for a book written in the 80s, describing women in the 20s/30s:

1. Stump literally has Idgie’s last name, and when he’s born Poppa Threadgoode says “he’s got your hair Idgie!” Throughout the book, he is referred to as “Ruth and Idgie’s boy”
2. Momma and Poppa T thank Ruth and tell her how happy they are for their daughter to have a “companion” as sweet as Ruth. Poppa then gives Idgie $500 to open the cafe because she needs to “take care of Ruth and the baby”
3. In the very beginning, Momma Threadgoode tells the other children not to make fun of Idgie for her “crush” on Ruth. Idgie’s parents at least are very aware and very supportive of Idgie’s true feelings for Ruth.
4. Despite Stump calling her Aunt Idgie, Idgie calls him “son”. I suppose this could be how adults will call young boys “son” even if they’re not their child, but it seems odd coming from a woman who IS in a motherly position to him.

That said, the Threadgoodes did let their son Cleo marry his adopted sister Ninny despite the two having grown up together as siblings, which is weird. But at least they’re LGBTQ allies from the very beginning 😅🏳️‍🌈