Thanks to Haribo, my daughter and I have had one of the important chats a little earlier than I'd expected.
Sucked in by the power of marketing, she wanted to buy sweets in the supermarket, but they were branded with TERF wizard school stuff, so I explained that we could buy sweets, but not those, and she obviously wanted to know why.
Thus we had a short chat in the supermarket about how there was a person who had created those characters who turned out to be a bully, and she would get money from anything sold that was to do with her work. Then in the car we had a longer chat about trans people in which I was very conscious that my way of explaining who they are might not be the best and I might be putting it badly, but it was better to have the talk now than not at all.
Her current stance is that she is not OK with bullies and has immediately accepted that we don't buy anything that gives them money, and she specifically says she is on the side of trans people because some of them are our friends. Which might not be the perfect motivation, but I'll take it.
Usefully, this also led to a shorter talk about how people should be allowed to love and marry who they like irrespective of gender, but mostly she was surprised that anyone would think otherwise.
Respect is so simple a 10 year old can grasp it.