I think it was the summer before high-school. I'm in a similar situation in that I work from home and can be flexible. DD is now 14.
I let her sort her down time, occasionally I suggest something if she's bored. When she was a bit younger she hated organising stuff with her friends directly - fear of rejection maybe. So she'd tell me to organise it with the parents. She's better at sorting her own plans out now, but still won't invite people to ours herself.
She's asked to do a summer school dance camp, which lasts a week and will keep her busy. But mostly she'll vegetate in her room on her phone or laptop, read, do school work - homework over the holidays, go in the garden to vegetate on her phone or read there, practice dancing, cook, bake, go into town with friends, video call with friends, meet up at the park/someone's house with anyone who's not on holiday. She also tends to challenge herself to learn new skills - examples from previous years are Spanish on dulingo, backbends, cartwheels, splits, knitting, rollerskating, skateboarding. Some are more successful than others!
But I would say that over 50% of the time is spent vegetating 🤣