Hi, all. After I upgraded the system and rebooted, the secondary ethernet port(i.e. the LAN port) is gone.
The system info: https://paste.armbian.com/ekotoqigos
nanopi-r4s:~:% ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever pre