Seems to be working fine at 2.5 GbE with r8125-9.003.04 and Ubuntu Mate 20.04 LTS. See:
https://forum.odroid.com/viewtopic.php?t=39323
For info here is my config on 6.9.1:
>>lspci -k | grep -iA3 net
01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller
Subsystem: Realtek Semiconductor Co., Ltd. Device 0123
Kernel driver in use: r8169
Kernel modules: r8169, r8125
>> modinfo r8169
filename: /lib/modules/5.10.21-Unraid/kernel/drivers/net/ethernet/realtek/r8169.ko.xz
firmware: rtl_nic/rtl8125b-2.fw
firmware: rtl_nic/rtl8125a-3.fw
firmware: rtl_nic/rtl8107e-2.fw
firmware: rtl_nic/rtl8107e-1.fw
firmware: rtl_nic/rtl8168fp-3.fw
firmware: rtl_nic/rtl8168h-2.fw
firmware: rtl_nic/rtl8168h-1.fw
firmware: rtl_nic/rtl8168g-3.fw
firmware: rtl_nic/rtl8168g-2.fw
firmware: rtl_nic/rtl8106e-2.fw
firmware: rtl_nic/rtl8106e-1.fw
firmware: rtl_nic/rtl8411-2.fw
firmware: rtl_nic/rtl8411-1.fw
firmware: rtl_nic/rtl8402-1.fw
firmware: rtl_nic/rtl8168f-2.fw
firmware: rtl_nic/rtl8168f-1.fw
firmware: rtl_nic/rtl8105e-1.fw
firmware: rtl_nic/rtl8168e-3.fw
firmware: rtl_nic/rtl8168e-2.fw
firmware: rtl_nic/rtl8168e-1.fw
firmware: rtl_nic/rtl8168d-2.fw
firmware: rtl_nic/rtl8168d-1.fw
license: GPL
softdep: pre: realtek
description: RealTek RTL-8169 Gigabit Ethernet driver
author: Realtek and the Linux r8169 crew <
[email protected]>
alias: pci:v000010ECd00003000sv*sd*bc*sc*i*
alias: pci:v000010ECd00008125sv*sd*bc*sc*i*
alias: pci:v00000001d00008168sv*sd00002410bc*sc*i*
alias: pci:v00001737d00001032sv*sd00000024bc*sc*i*
alias: pci:v000016ECd00000116sv*sd*bc*sc*i*
alias: pci:v00001259d0000C107sv*sd*bc*sc*i*
alias: pci:v00001186d00004302sv*sd*bc*sc*i*
alias: pci:v00001186d00004300sv*sd*bc*sc*i*
alias: pci:v00001186d00004300sv00001186sd00004B10bc*sc*i*
alias: pci:v000010ECd00008169sv*sd*bc*sc*i*
alias: pci:v000010FFd00008168sv*sd*bc*sc*i*
alias: pci:v000010ECd00008168sv*sd*bc*sc*i*
alias: pci:v000010ECd00008167sv*sd*bc*sc*i*
alias: pci:v000010ECd00008161sv*sd*bc*sc*i*
alias: pci:v000010ECd00008136sv*sd*bc*sc*i*
alias: pci:v000010ECd00008129sv*sd*bc*sc*i*
alias: pci:v000010ECd00002600sv*sd*bc*sc*i*
alias: pci:v000010ECd00002502sv*sd*bc*sc*i*
depends:
retpoline: Y
intree: Y
name: r8169
vermagic: 5.10.21-Unraid SMP mod_unload
>> ethtool eth0
Settings for eth0:
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
2500baseT/Full
Supported pause frame use: Symmetric Receive-only
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
2500baseT/Full
Advertised pause frame use: Symmetric Receive-only
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Link partner advertised link modes: 100baseT/Half 100baseT/Full
1000baseT/Full
2500baseT/Full
Link partner advertised pause frame use: Symmetric
Link partner advertised auto-negotiation: Yes
Link partner advertised FEC modes: Not reported
Speed: 2500Mb/s
Duplex: Full
Auto-negotiation: on
master-slave cfg: preferred slave
master-slave status: slave
Port: MII
PHYAD: 0
Transceiver: external
Supports Wake-on: pumbg
Wake-on: d
Link detected: yes
>> ethtool -i eth0
driver: r8169
version: 5.10.21-Unraid
firmware-version: rtl8125a-3_0.0.1 08/24/19
>>lspci -v | grep RTL
01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller
>> /sys/class/net/eth0/device/driver# ls -l
...
module -> ../../../../module/r8169/
>>lshw -C network
*-network
description: Ethernet interface
product: RTL8125 2.5GbE Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:01:00.0
logical name: eth0
version: 00
capacity: 1Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd bus_master cap_list rom ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=5.10.21-Unraid duplex=full firmware=rtl8125a-3_0.0.1 08/24/19 latency=0 link=yes multicast=yes port=MII promiscuous=yes