Step 1 :

Please read 2021_04_29_UpgradeFirmwareETH0_v1_1 inside the zip file (ETH0_firmware directory)

Step 2 :

Please read Note_SBT_CT_18-25_UpgradeFirmware_Agiliplug_CABTR_V2.3 inside the zip file (ETH1_firmware directory)