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.
Highly phone dependent. Some phones have an official process, others have hacks, many others have fuck all.