Really like the one-handed phone form factor, but the Box Palma being WiFi only was a deal breaker for me.
Instead I got a Hisense A5 from eBay for ~$130 and after rooting, debloating, and installing E-ink optimized versions of Open source android apps it's a perfect companion for my Boox Nova Air C. With KOReader syncing across devices.
The instructions are not official, but there are some good community ones https://forum.xda-developers.com/t/hisense-a5-pro-cc-how-to-root-unlock-bootloader.4109021/post-88755703
Bit of warning though, they're using a variant of the A5, not a base A5. The CVE and exploit code in the link should still work (if not patched) but the image files will certainly not, and will fuck up your device if you try to flash images made for a different device, even a variant.