Important
The SD transfer use the GCODE protocol based on M28/M29 commands, this protocol is often broken by external queries or even auto reporting. Additionnaly the SD transfer is very slow: ~0.4KB/s, which make it almost unusable.
So this protocol is no more supported in ESP3D, and feature is provided as it is
.
The only existing reliable solution to be used in addition of ESP3D 2.1X, is to use a WiFi SD card like Toshiba FlashAir, which is no more produced.
ESP3D 3.0 has some existing solution and some ongoing plan for better SD support depending on hardware used.