I had a hiccup installing Android 10, could have been a fluke or mistake on my end, so feel free to try. I was able to get the latest version of 8.1 from the above thread to work. Specifically, from here: https://github.com/phhusson/treble_e...leases/tag/v32, I chose the system-arm64-aonly-gapps-su.img.xz link.
Update: sergio_chichi has confirmed a 9.0 image working here: https://forum.xda-developers.com/sho...9&postcount=32
Step 1: Download Sugar. This thread: https://forum.xda-developers.com/and...phone-t4021201, has everything you need to know about Sugar. I ran the upgrade once to download the full stock ROM (make a backup as described). Warning, this erases all of your data.
Step 2: Follow this guide: https://forum.xda-developers.com/and...ource-t3843473, to build a TWRP for the Palm Phone without source. I used the latest TWRP for the Asus Nexus 7 2013 LTE as my base. From your Palm upgrade backup, the recovery image is the one that starts with 'R', about 36MB. Rename your new TWRP image to match the stock recovery and replace it similar to the rooting guide for replacing the boot image.
Update: snoopy20 has shared his TWRP image here: https://forum.xda-developers.com/sho...3&postcount=26
Step 3: Extract the system image you downloaded and rename and replace the stock system image. It's the largest file in your Sugar device folder.
Step 4: Re-run the upgrade in Sugar with your replaced images in place.
Step 5: You're probably stuck in a boot loop. Press and hold the power button until you get into recovery, which is now TWRP. First, I formatted data. Then push (NOT sideload, since the zip relies on its own name to configure the flash) this zip: https://forum.xda-developers.com/and...crypt-t3817389 and install it from TWRP. The stock configuration should be fine, i.e. don't worry about re-naming the zip.
Step 6: Reboot! Wipe data and cache for good measure, and you should be set!
All credit goes to the folks from the links above for creating the Treble system image, TWRP guide, and dm-verity script. Thanks to snoopy20 for his TWRP image.
Things that work so far:
* Almost everything
* Soft key does nothing, should be mappable via an app?
* Screen auto brightness?