[6.10.0-RC1] Intel X550-T2 cannot auto negotiate 2.5Gbit link

LAN adapter: Intel X550-T2

Switch: TP-Link TL-SG108-M2

[8086:1563] 07:00.0 Ethernet controller: Intel Corporation Ethernet Controller 10G X550T (rev 01)

[8086:1563] 07:00.1 Ethernet controller: Intel Corporation Ethernet Controller 10G X550T (rev 01)

Asus XT8 access point can successfully negotiate 2.5Gbit link on the switch, but the Intel X550-T2 only negotiates 1Gbit, 2500baseT/Full and 5000baseT/Full are listed as supported but are not advertised:

root@Mammuth:~# ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   100baseT/Full
                                1000baseT/Full
                                10000baseT/Full
                                2500baseT/Full
                                5000baseT/Full
        Supported pause frame use: Symmetric
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  100baseT/Full
                                1000baseT/Full
                                10000baseT/Full
        Advertised pause frame use: Symmetric
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Speed: 1000Mb/s
        Duplex: Full
        Auto-negotiation: on
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: internal
        MDI-X: Unknown
        Supports Wake-on: d
        Wake-on: d
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes

Manually setting link speed with ethtool -s eth0 speed 2500 duplex full successfully sets the link to 2.5Gbit:

root@Mammuth:~# ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   100baseT/Full
                                1000baseT/Full
                                10000baseT/Full
                                2500baseT/Full
                                5000baseT/Full
        Supported pause frame use: Symmetric
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  2500baseT/Full
        Advertised pause frame use: Symmetric
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Speed: 2500Mb/s
        Duplex: Full
        Auto-negotiation: on
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: internal
        MDI-X: Unknown
        Supports Wake-on: d
        Wake-on: d
        Current message level: 0x00000007 (7)
                               drv probe link
        Link detected: yes

Everything works correctly but is not persistent after reboot, solved by adding commands in the go file to set ports speed at boot:

root@Mammuth:/boot/config# cat go
#!/bin/bash
# Start the Management Utility
/usr/local/sbin/zenstates --c6-disable
/usr/local/sbin/emhttp &
ln -s /boot/scripts/diskmv /usr/sbin
ln -s /boot/scripts/consld8 /usr/sbin
/usr/sbin/ethtool -s eth0 speed 2500 duplex full
/usr/sbin/ethtool -s eth1 speed 2500 duplex full

Had this issue in Archlinux as well and it was fixed in June 2021 with the Network Manager 1.32 release.