I sure see lots of retired cell phones and wonder why I haven't seen any
homebrew projcts to make something useful out of old outdated ones.


What kind of projects did you have in mind?

These days with DigiKey, Mouser, etc. it's often easier just to design
something from scratch, and that way anyone can build it (rather than trying
to track down a specific model phone...).
================================
Old cell phones and other SMD stuffed equipment are excellent for
self-training in SMD soldering ,before engaging in a project.
remove --- clean pads --- inspect with 8times magnif.glass
---resolder ----- inspect ----- if necessary remove solder bridges
-----inspect ------ DONE

Frank KN6WH / GM0CSZ