Worked!
First, I opened tftpd and found this log:
Connection received from 192.168.1.1 on port 3599 [30/06 20:15:46.003]
Read request for file <openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb>. Mode octet [30/06 20:15:46.004]
File <openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb> : error 2 in system call CreateFile O sistema não pode encontrar o arquivo especificado. [30/06 20:15:46.005]
The router seemed to be looking for this file openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-ubootmod-initramfs-recovery.itb - I downloaded, put in the tftpd folder, started tftp, powered up the router and uploaded to the router. Router rebooted and SSH was back. I followed the debrick tutorial (point 7) but I got an error:
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt SNAPSHOT, r26815-b4069fad02
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# ubidetach -p /dev/mtd8
root@OpenWrt:~# ubiformat /dev/mtd8 -y -f /tmp/openwrt-mediatek-filogic-xiaomi_mi-router-ax3000t-initramfs-factory.ubi
ubiformat: mtd8 (nand), size 117440512 bytes (112.0 MiB), 896 eraseblocks of 131072 bytes (128.0 KiB), min. I/O size 2048 bytes
libscan: scanning eraseblock 895 -- 100 % complete
ubiformat: 896 eraseblocks have valid erase counter, mean value is 7
ubiformat: flashing eraseblock 62 -- 100 % complete
ubiformat: formatting eraseblock 895 -- 100 % complete
root@OpenWrt:~#
root@OpenWrt:~# reboot
root@OpenWrt:~#
After this reboot, router back to the first state and nothing happens. I cannot access via SSH or web.