Any used PC/NUC/Intel Atom board is much, much faster and some cost around the same.
Again, mainly just for fun and experience.
The Raspberry 4 at 1 Gflops/watt is a better option if you want to power the thing with lead acid batteries as backup power for more than 24 hours.
Also Raspberry 4 can be cooled passively with a smaller heatsink so the total size and weight is less.
An Intel compute stick or beelink mini pcs are also passively cooled and weigh no more.
The Raspberry 4 is peak power efficient: http://web.eece.maine.edu/~vweaver/group/green_machines.html
Mobile phones don't have a keyboard, you can only consume with them. I produce things.
Those sticks don't have a company with it's own GPU and linux (Raspbian now RaspberryOS) behind them and they cost more per watt for performance I don't need.
However I have 2x NUC with Streacoms passive case: https://streacom.com/products/nc2-fanless-chassis/
The person probably enjoyed doing it, most likely didn’t harm anyone in the process, and possibly learnt some things on the road.
Not everything need to be useful beyond the joy of doing it.