ip rule fwmark doesn't work about bpi-m2u-bsp HOT 1 OPEN

It's not working because the default route you added is at the wrong table, you are adding it to the main table instead of table 1.

Here's my terminal output (Arch Linux 5.6.7-arch1-1)

#ip rule add to 1.1.1.1 fwmark 1 table 1
#ip rule
0: from all lookup local
32765: from all to 1.1.1.1 fwmark 0x1 lookup 1
32766: from all lookup main
32767: from all lookup default
# ip route get 1.1.1.1
1.1.1.1 via 192.168.42.129 dev enp0s4f1u5 src 192.168.42.143 uid 0
cache
# ip route get 1.1.1.1 mark 1
1.1.1.1 via 192.168.42.129 dev enp0s4f1u5 src 192.168.42.143 mark 1 uid 0
cache

As you could see it's not working
but when I add the default route

# ip route add default via 192.168.1.1 table 1
# ip route get 1.1.1.1 mark 1
1.1.1.1 via 192.168.1.1 dev enp3s0 table 1 src 192.168.1.254 mark 1 uid 0
cache
# ip route get 1.1.1.1
1.1.1.1 via 192.168.42.129 dev enp0s4f1u5 src 192.168.42.143 uid 0
cache

it wasn't working because it was using the backup main table

from bpi-m2u-bsp.