I'm not aware of any distro that allows you install Debian natively on Android tablets, but there's userland which allows you to run Debian from within Android:
I've done this with a few old phones. There's a couple tools you can use, even on a non-rooted phone, to run a Linux environment.
https://userland.tech/download/
Also, grab Aurora Droid. You can install that as a side loaded APK. It's a third party app manager that can pull from open source repos like F Droid, Guardian Project, Kali, etc.
UserLand is an opensource app that might fit your needs. No root, run linux apps, it's in fdroid and play store
A full blown OS replacing Android doesn't exist anymore. PostmarketOS is trying but most phone models don't even have modem support.
There is this: https://userland.tech/
There is no good way though, most ways are terminal only and those that arnt only do unaccelerated graphics over a loopback network connection and lack sound completely, so no games.
There used to be xserver xsdl which dident have those limits(graphics was still wernt hardware accelerated though) but it broke around Android 6.
Linux Deploy was updated last month?