Thanks for both suggestions, I will try out both.
The platformio plus option, is less attractive, as it requires internet as far as I understand.
In the countryside (in Chile) Internet is often a problem, relying on 3G modems, so one still has to go with PC to the field, connect to the router and upload arduino sketches via raspberries.
So a simple target /upload command on pio, that just takes the hex file and upload it, would still be nice.
Using avrdude requires more detailed knowhow and understanding of a load of parameters, which is an option, but Pio is suppossed to simplify these manual procedures. Maybe stuff for the pio team to consider.