Kubuntu：ネットワークカードが100Mbpsモードで停止しました。

複数のケーブルを試してみましたが、NIC / OSに問題があると確信しています。私のマザーボードのネットワークカードは1Gbpsをサポートしていますが、ホームプラグ（Devolo Magic 2 Wifi、deffoはGBイーサネット対応）に接続すると、常に100Mbpsモードで接続されているようにKDE OSシステムトレイアイコンに表示されます。

以下のifconfigを実行しました。

enp5s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.50.2  netmask 255.255.255.0  broadcast 192.168.50.255
        inet6 fe80::7285:c2ff:fec8:1023  prefixlen 64  scopeid 0x20<link>
        ether 70:xx:xx:xx:xx:23  txqueuelen 1000  (Ethernet)
        RX packets 138995  bytes 119279125 (119.2 MB)
        RX errors 0  dropped 142  overruns 0  frame 0
        TX packets 201518  bytes 233657407 (233.6 MB)
        TX errors 6  dropped 0 overruns 0  carrier 2  collisions 7086

lspci -v:

05:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15)
        Subsystem: ASRock Incorporation Motherboard (one of many)
        Flags: bus master, fast devsel, latency 0, IRQ 36
        I/O ports at f000 [size=256]
        Memory at f7504000 (64-bit, non-prefetchable) [size=4K]
        Memory at f7500000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit+
        Capabilities: [70] Express Endpoint, MSI 01
        Capabilities: [b0] MSI-X: Enable+ Count=4 Masked-
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [140] Virtual Channel
        Capabilities: [160] Device Serial Number 23-10-c8-c2-85-70-00-00
        Capabilities: [170] Latency Tolerance Reporting
        Capabilities: [178] L1 PM Substates
        Kernel driver in use: r8169
        Kernel modules: r8169

GbEモードで動作させる方法についての手がかりはありますか？

ethtool enp5s0 | grep Speed

Cannot get wake-on-lan settings: Operation not permitted
        Speed: 100Mb/s

ethtool enp5s0 ...

Settings for enp5s0:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/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 
        Advertised pause frame use: Symmetric Receive-only
        Advertised auto-negotiation: No
        Advertised FEC modes: Not reported
        Speed: 100Mb/s
        Duplex: Half
        Port: MII
        PHYAD: 0
        Transceiver: internal
        Auto-negotiation: off
Cannot get wake-on-lan settings: Operation not permitted
        Current message level: 0x00000033 (51)
                               drv probe ifdown ifup
        Link detected: yes

ありがとうございます。