Ask HN: Devices to allow children to listen to podcasts on my local network?

Does anyone have advice for a device I could lock down that would allow my children to listen to podcasts I've downloaded to my local network using Audio Bookshelf? So far the best I've been able to come up with is to buy a cheep Android phone, install the Audio Bookshelf app, and configure my network to not allow the device to access the internet. The only issue with this plan is that as far as I can tell there's no easy way to only install the Audio Bookshelf app, and remove all other apps. While if the device does not have internet access I'm not concerned about them poking around in the email, calendar, etc it'd be nice if there were fewer distractions. I'm an iOS user so may be missing something involving Android and third party launchers or device controls.