I used the latest build of Orange pi 5b. The strange point is our ethernet inteface is "end1" while normally it should be "eth0".
By the way, I tried other solution by editting the file /etc/network/interfaces and it seems to work well up to now.
@OttawaHacker Thank you for sharing the solution. I just followed your guide and it worked after first reboot.
By the way, later on, after several other reboot, the mac is reset again.
Do you have any other suggesstion to fix?
Thank you.