A big topic was Jane Austen vs. the Regencies and other modern works set in the Regency era. Jane Austen wrote about the gentry, not about the nobility. And certainly not about the upper levels of the nobility.
Also Austen's female centric world, when so many men were off fighting, vs. boy's fiction, of the Horatio Hornblower variety -- very split up because society was.
It was also an era of social change. The French Revolution did have its reverberations, and people were rising more often. (Remember Persuasion?) Plus the power moving from the king to the nobility and spreading out. This was helped by the massive disreputability of the royal families. The Regent himself, of course, tried to divorce his wife, and his brothers shacked up and produced bastards by the dozens until it was clear there would be no heir from the Regent and so they scrambled to marry. One aspect of Queen Victoria was her respectabilty and, ehem, Victorianism that helped make the royal family presentable again.
Then, Queen Victoria also married in a love match. The Regency was the era in which the notion that upper-crust marriage was all about the property was giving way to the notion of love matches. In the Victorian times, it was suitable for a woman to forget wealth and marry for love. In the Regency, they were still up in the air about whether that was proper or not.
Two panelists had read another book by the author of Shades of Milk and Honey and only after discussing it remembered that it wasn't out yet.
Some talk about what technological changes there were. The one I remember was the heliograph, which was running all over Europe, lost in the Napoleonic Wars, and never got going again before the telegraph was in place. It did, after all, require an extensive network, and make an obvious military target, and they didn't have the industrial capacity to restore it easily.
I brought up that Queen Victoria ascended the throne because the brother older than her father married and had a whole passel of kids -- who all died in childhood. It was a time of poor medicine. And one reviewer on the panel riffed on the doctor heroes in Regencies and how implausible it was, and how surgeons were not the cream of the crop but an even lower occupation group. Gentlemen became physicians. And for some reason, the fictional doctors always took it into their heads to be very, very, very clean.