I have a Toshiba Satellite L875D-S7210 with a Realtek 10/100 ethernet adapter. It uses the re(4) driver. I'm running FreeBSD 13-RC5. My ethernet connection may work for a few hours just fine, but it will randomly drop the connection. ifconfig will report "no carrier", and dmesg and /var/log/messages will contain thousands of "re0: PHY read failed" errors. Restarting the netif service won't bring the connection back up. using ifconfig to bring the device down and back up won't work. Even a warm reboot won't bring the ethernet connection back up. I have to completely power down the system then turn it back on to get the ethernet working again. On a warm reboot, FreeBSD won't even recognize that the ethernet adapter is there after a failure. I Googled the error, and there are reports of similar behavior with the re driver going back to 2008, so this may be a longstanding issue.

Also, my wifi connection will intermittently go out. But with the wifi, restarting the netif service brings the connection back up. It was actually the wifi issue that made me start using ethernet so I could try to keep a stable connection. I mention the wifi dropping for two reasons: 1) I had Manjaro Linux on this same laptop for months before putting FreeBSD on it, and I never had any problems with the wifi connection, and 2) if my laptop is connected to wifi and ethernet at the same time, when the connection drops, it simultaneously drops the wifi and the ethernet connection. So there seems to be some relationship between the two where a failure in one causes the other to fail.