I'd tried several times, there's a video supplied talking about this model in your support but doesn't work at all.
[EDL] UNLOCK BOOTLOADER Selected Model : Xiaomi Redmi Note 8T
Code Name : Willow
Operation : Unlock Bootloader [1]
Authenticating... OK
Retrieving data... OK [507,87 KiB]
Initializing data... OK
Searching for HS-USB QDLoader 9008... COM10
Connection : USB 2.0 High-Speed
USB Driver : [Qualcomm Incorporated] qcusbser - Version : 2.1.1.2
Connecting to device... OK
Handshaking... OK
Reading bootloader info... OK
Serial : 3314718123 SoC : [Snapdragon 665] [SDM665] [0x0010A0E1]
OEM : Xiaomi [0x0072] Model : Unknown [0x0000]
PK_HASH[0] : 1BEBE3863A6781DB4B01086063007334
PK_HASH[1] : DE9E5CA14971C7C4F4358EC9D79CDA46
Writing flash programmer... OK
Connecting to flash programmer... OK
Configuring device... OK
Firehose config : eMMC [Sector:512] [Target:0] [Host:16384]
Reading partition map... OK - LU Count : 1
Reading info... OK
Model Name : Redmi Note 8T
Product Name : willow
Manufacturer : Xiaomi
Platform : willow
Android Version : 11
Security Patch : 2021-12-01
Build : V12.5.2.0.RCXMIXM
Build Date : Mon Dec 27 20:29:39 CST 2021
MIUI Version : V125
MIUI Build : V12.5.2.0.RCXMIXM
Processing LUN0 - rawprogram0.xml
Writing unlocktool1->unlocktool1... OK
Writing unlocktool1->unlocktool1... OK
Writing unlocktool2->unlocktool2... OK
Writing unlocktool2->unlocktool2... OK
Writing unlocktool3->unlocktool3... OK
Writing unlocktool3->unlocktool3... OK
Rebooting to FASTBOOT... OK
UNLOCKTOOL 2022.01.19.0
Elapsed time : 22 seconds
After unlock bootloader by testpoint, reconected in fastboot and
Task
Key Value
Variant SM_ EMMC
Bootloader Unlocked no
Serial No 1a2e81f10013
Secure Boot yes
Product laurel_sprout
Parallel Flash yes
Kernel uefi
Hardware Rev 10000
Battery Volt 3937
Download Size 804276224
UNLOCKTOOL 2022.01.19.0
Elapsed time : 0 seconds
The phone is in V12.5.2.0.RCXMIXM_20211227.0000.00_11.0_global
[EDL] UNLOCK BOOTLOADER Selected Model : Xiaomi Redmi Note 8T
Code Name : Willow
Operation : Unlock Bootloader [1]
Authenticating... OK
Retrieving data... OK [507,87 KiB]
Initializing data... OK
Searching for HS-USB QDLoader 9008... COM10
Connection : USB 2.0 High-Speed
USB Driver : [Qualcomm Incorporated] qcusbser - Version : 2.1.1.2
Connecting to device... OK
Handshaking... OK
Reading bootloader info... OK
Serial : 3314718123 SoC : [Snapdragon 665] [SDM665] [0x0010A0E1]
OEM : Xiaomi [0x0072] Model : Unknown [0x0000]
PK_HASH[0] : 1BEBE3863A6781DB4B01086063007334
PK_HASH[1] : DE9E5CA14971C7C4F4358EC9D79CDA46
Writing flash programmer... OK
Connecting to flash programmer... OK
Configuring device... OK
Firehose config : eMMC [Sector:512] [Target:0] [Host:16384]
Reading partition map... OK - LU Count : 1
Reading info... OK
Model Name : Redmi Note 8T
Product Name : willow
Manufacturer : Xiaomi
Platform : willow
Android Version : 11
Security Patch : 2021-12-01
Build : V12.5.2.0.RCXMIXM
Build Date : Mon Dec 27 20:29:39 CST 2021
MIUI Version : V125
MIUI Build : V12.5.2.0.RCXMIXM
Processing LUN0 - rawprogram0.xml
Writing unlocktool1->unlocktool1... OK
Writing unlocktool1->unlocktool1... OK
Writing unlocktool2->unlocktool2... OK
Writing unlocktool2->unlocktool2... OK
Writing unlocktool3->unlocktool3... OK
Writing unlocktool3->unlocktool3... OK
Rebooting to FASTBOOT... OK
UNLOCKTOOL 2022.01.19.0
Elapsed time : 22 seconds
After unlock bootloader by testpoint, reconected in fastboot and
Task
Key Value
Variant SM_ EMMC
Bootloader Unlocked no
Serial No 1a2e81f10013
Secure Boot yes
Product laurel_sprout
Parallel Flash yes
Kernel uefi
Hardware Rev 10000
Battery Volt 3937
Download Size 804276224
UNLOCKTOOL 2022.01.19.0
Elapsed time : 0 seconds
The phone is in V12.5.2.0.RCXMIXM_20211227.0000.00_11.0_global