after asking for read and write permission; I proceed to carry out through AppendToFile, the addition of various components within a CSV file .. obviously in the internal memory. Searching the community faqs; I read that up until a few years ago, it was not possible to be able to save inside a portable MicroSD, since it is a read-only memory. Is there any news on this right now?
this information is up-to-date, see also Some basics on Android storage system
2.2. External (removable / micro) SD card
There may also be another External Storage: a removable (micro) SD card, eg:
that can only be read (on devices with Android ≥ 4.4 /
KitKat, API 19).