My iPad only lasts a few days even with zero use. I have not been able to figure out what settings to modify so that I can (for example) pick it up a month later and not find the battery dead.
Disable push notifications and background sync. Those will always be the things that pull the most idle power.
I have the same issue. I've disabled "Find My" feature and uninstalled everything that kept showing up as battery draining apps. My iPad loses about 20-25% of battery every night and there is nothing showing up in battery details anymore.
I'm pretty sure the problem would go away with a factory reset. Just like it with old Windows installations, except you had a better change debugging those...
Harsh suggestion: log out of iCloud on the device.
If that works you can try to isolate it further.
My new A16 iPad seems to use more power sitting closed much than I would have thought. I came here to say this, but found you got to it first. I hope someone here has some thoughts on the matter.
I am more Android guy, so I am not yet familiar with the options. Does the iPad have a power usage app describing what apps/services are using the power? Bluetooth for one to keep the Apple Pencil ready, I suppose.
It's Find My. No great solution. I turn my iPad off now when not actively using it.