Hi @RadxaYuntian ,
On a fresh Rock5B installation, if I understand correctly, the onboard Ethernet controller comes unconfigured right?
I.e. DHCP client has not been pre-set for it.
That there is no configuration is evidenced by that the /etc/NetworkManager/system-connections/ directory is empty.
I am quite sure that DHCP client was default behavior before, so I guess you changed it recently.
Thanks