Junior S&S Isa, where shall I go?

Sorry if this has been covered but new to Reddit.

Expecting our first child in 8 weeks and want to get a junior ISA set up ASAP. Where do people recommend I go? Looking for a simple index tracker I think. I currently use JP Morgan for mine and my partners ISA and they do junior ISAs but thought I’d check what else is out there.

Planning on maxing out the £9k allowance each year.

Thank you!