You need to send an email to
service@deye.com.cn with the model, current FW & serial number of your inverter to receive an upgrade.
They do not send you a file but do the firmware upgrade remotely thru Solarman.
Note that they will not tell you when they will do the upgrade (they did just a few hours after I asked them) & at the time your inverter will turn off & you will don't have power for a few minutes ...