A used Google Pixel or Samsung Galaxy should be pretty cheap. Just make sure they support whichever version of Android you want to develop on. Pixel 6’s are under $200 USD on eBay currently and should all be upgradable Android 14.

Krita is pretty good.

You need Windows installed first, set up your partitions, then install Linux. You could backup your data and then restore it. That’s the easiest way if you choose not to use a windows vm.