Beryl AX eth0 negotiation issues - consistent up/down. How to specify interface/link speed?

Routers
14

I've also been having this issue with eth0 (2.5Gbps) and the only way I could fix this was to change wan port to eth1 (see [1] ).

[1] GL-MT3000 WAN interface eth0 going up and down - #11 by Ndv