Just confirming that the default Ethernet RX/TX flow is off by default in 23.05.0 (while in 22.03.5 it was auto-negotiated).
I've managed to revert to previous behavior by installing ethtool and creating the file /etc/hotplug.d/iface/06-ethenableflowcontrol with the following contents:
#!/bin/sh
logger "enabling-eth-flow-control-from-hotplug"
ethtool -A eth0 autoneg on rx on tx on
ethtool -A eth1 autoneg on rx on tx on