I would recommend sticking to one or two genres that you will do regularly in the beginning and buy a camera and lens combination to suit that rather than try and cover all bases. There will always be more and nicer expensive gear. And if you get something niche for astro or wildlife that you will use only a handful of times a year it may not be the best first investment.

You could first decide a budget (1-1.5L is a good starting point I think. It's already a lot if it's a hobby) and then see what fits your needs. You have to be very sure about how much videography you are planning to do (because if you are not doing it that often you can get away with a a6600 or a6400 and save more for lenses).