I tried several different firmware files with web recovery. These are not working. I have web recovery version:
ZBT MT7981 Uboot V2.0 FIRMWARE UPDATE
U-Boot 2023.07 (Oct 31 2023 - 22:47:03 -0700)
I can recovery my router only with original ZBT firmware version:
Z8102AX-eMMC-mt7981-24 0117_185433.bin ( https://file.io/xfzaG85WInZ9 )