My experience is that 2.5 to 3.5 years old is "average" with some kids before and after that age.
Not having interest at 24 months is normal. (Toilets are interesting though!) In your shoes, I might let her hang around in the garden without knickers on in the summer and see if that sparks at interest but don't worry if it's 2019 before she's ready.
My daughter turned 2 in November and she's point blank refusing to use the potty. She will sit on it for a minute or so but soon starts to scream and cry We've not been forcing her into it but trying to let her know if she needs to wee or poo she can do it on the potty. Should I be worried that she has no interest?