It’s finally all back to normal.
Here is the full investigation.
basically the root cause was the file
/etc/fw_env.config
As spotted here and there, it seems the expected values would be /dev/mtd0 0xF0000 0x10000 0x10000 but after checking with the command
cat /proc/mtd
dev: size erasesize name
mtd0: 000f0000 00010000 “U-Boot”
mtd1: 00700000 00010000 “Rescue system”
mtd2: 00010000 00010000 “u-boot-env”
u-boot-env is actually located on mtd2.
I then updated /etc/fw_env.config with the following values :
/dev/mtd2 0x00000 0x10000 0x10000
and with that, the command fw_printenv is fixed and then allow to update the U-Boot without any issues :
strings /dev/mtd0 | grep “U-Boot” | head -1
U-Boot SPL 2024.10-rc3-OpenWrt-r20343+127-4e1d1b7df0 (Sep 13 2024 - 01:38:50 +0000)
Hope it will help those facing the same issue!