AOSP-based Android 9 Pie ROMs are now available for the eight-year old HP TouchPad thanks to the efforts of the custom ROM community. The HP TouchPad, abandoned soon after release, originally ran webOS but was quickly adopted by enthusiasts who managed to successfully port several Android OS versions to the tablet. While certain functionality such as Bluetooth and Camera are still being worked upon, testers claim that the tablet is able to run the latest Android update just as new.
https://www.notebookcheck.net/New-wine-in-old-bottle-The-good-ol-HP-TouchPad-gets-a-working-Android-9-Pie-custom-ROM.419766.0.html