It's not a phone?
In 2025, the Palma product seems like feature creep since I wouldn't expect smartphone apps to appeal to anyone looking for less distraction. That's how most people use tablets which are dedicated distraction devices stuck on wifi.
The HMD fusion budget smartphone has a pogo-pin port on the back for peripherals https://www.theregister.com/2025/01/03/hmd_fusion_review/
Not sure why they fail in the marketplace. Maybe look at other similar market failures like power tools with different interchangable heads? I suspect the sticker price of the individual modules scares consumers.