I have 2 of 5 ethernet ports broken on my RB 750UP. After diagnosis with multimeter and oscilloscope all the electric cirlce from SoC to cable pins I replaced the incoming filter H7201DG but ports still not working yet. For that reason I decided to replace SoC Atheros AR7241-AH1A.
I know that first 64 KB of flash contains bootloader also it contains serial number, MACs and other critical things and cause that I understand that my MikroTik license after SoC replacement shall be gone.
1. Does anybody know how to prevent license deactivation except going to service center (cause shipping to the service center costs more than new RB)?
2. What issues can I get after SoC replacement (except license deactivation)?

If you only replace the SoC (not the flash) and solder it well (without damage to the board) - I think it should work fine. I don't think this SoC itself contains any serial number.

I don't think this SoC itself contains any serial number.

But what about the MAC-addresses?