I decided to go back to the vendor firmware of my Linksys E8450.
I have followed the guide on github https://github.com/dangowrt/owrt-ubi-installer?tab=readme-ov-file#restoring-the-vendorofficial-firmware
But I forget to backup the vendor bootchain files and now I can't get the flies because i had reinstall openWRT many times.
Are they have another option to restore to the vendor firmware without vendor bootloader files or someone can share me vendor backup files?