Unable to use mobile data on Sony Xperia 10 III 4.4.0.64

I suggest aggregating the experiences and solutions and propose the following format:
“Land”, “Home/Roaming”

  • “Provider”, “OS Version”, “Model”: Solution → Speed
    Please put “?” in front if unsure, and “?” if unknown.

Spain, Roaming:

  • ?Movistar, ?v4.0.1, Xperia 10: no problems → ?/?

Switzerland, Home:

  • Salt, v4.4,0.72, Xperia 10 III: Remove SIM Card PIN → LTE 150/45
  • Salt, v4.4,0.72, Xperia 10 II: no problems → LTE 150/45