A fix is coming, but data analytics giant Palantir says it’s ditching Android devices altogether because Google’s response to the vulnerability has been troubling.
It's only compatible with modern Pixel devices, so unless you're old tablet is a Google Pixel Tablet, you can't install it anyway. But the installer is super easy to use (if you have a compatible device). It's literally all in your web browser.
It's an old Xperia Z4 and there's a few custom images on the forums. But the "how to" suggest using a tool that does not even exist in that version and is otherwise so sparse on information that I gave up after that.
I don't recommend installing random builds from forums like XDA. GrapheneOS definitely doesn't have an official version for anything other than Pixels, you might want to try LineageOS if you want to throw the tablet out anyway
Well, yes - what else am I going to install a custom rom on other than a device that is no longer receiving actual system updates but still works fine?
And as I said, there are a couple roms on the forums, just with very lacking installation instructions.