Recently i've moved from a desktop PC to a laptop device. Laptop came originally with Windows pre-installed so i didn't wanted to lose it. I changed in BIOS the HDD from RAID to AHCI and installed with DualBoot. Everything seems to work perfectly except the download speed (both on WiFi and LAN).

Tests done

• Speedtest.net over WiFi - laptop/Ubuntu: ~40MB download / ~400MB upload
• Speedtest.net over LAN - laptop/Ubuntu: ~30MB download / ~400MB upload
• Speedtest.net over LAN - laptop/Windows: ~300MB download / ~400MB upload
• Speedtest.net over LAN - laptop/CentOS Live CD: ~300MB download / ~400MB upload
• Speedtest.net over LAN - PC/Ubuntu 18LTS: ~300MB download / ~400MB upload
• scp (copy via LAN) - PC -> laptop: ~8MB speed

• scp (copy via LAN) - laptop -> PC: ~100MB speed

  03:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15) Subsystem: Dell RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller Flags: bus master, fast devsel, latency 0, IRQ 16 I/O ports at 3000 [size=256] Memory at c2404000 (64-bit, non-prefetchable) [size=4K] Memory at c2400000 (64-bit, non-prefetchable) [size=16K] Capabilities: Kernel driver in use: r8169 Kernel modules: r8169, r8168

  04:00.0 Network controller: Qualcomm Atheros QCA9377 802.11ac Wireless Network Adapter (rev 31) Subsystem: Dell QCA9377 802.11ac Wireless Network Adapter Flags: bus master, fast devsel, latency 0, IRQ 139 Memory at c2000000 (64-bit, non-prefetchable) [size=2M] Capabilities: Kernel driver in use: ath10k_pci Kernel modules: ath10k_pci

  Linux version 5.0.0-27-generic (buildd@lgw01-amd64-031) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #28~18.04.1-Ubuntu SMP

I've tried updating OS, different drivers (r8168-dkms, r8169), changing MTU, disabled IPv6 and other suggested changes but none of them worked.

Seems like i'm out of ideas and luck. Any advice is appreciated.

EDIT 1

It seems like Windows and Ubuntu uses the same SSID over Wifi - but it's still unclear why download is limited through both Wifi and LAN.

SSID used under Windows

SSID 5 : MyNetwork
Network type            : Infrastructure
Authentication          : WPA2-Personal
Encryption              : CCMP
BSSID 1                 : e4:8d:8c:f2:ab:57
     Signal             : 90%
     Radio type         : 802.11n
     Channel            : 9
     Basic rates (Mbps) : 1 2 5.5 11
     Other rates (Mbps) : 6 9 12 18 24 36 48 54
BSSID 2                 : e4:8d:8c:f2:91:3b
     Signal             : 100%
     Radio type         : 802.11n
     Channel            : 8
     Basic rates (Mbps) : 1 2 5.5 11
     Other rates (Mbps) : 6 9 12 18 24 36 48 54

SSID used under Ubuntu:

wlp4s0    Scan completed :
      Cell 01 - Address: E4:8D:8C:F2:91:3B
                Channel:8
                Frequency:2.447 GHz (Channel 8)
                Quality=70/70  Signal level=-35 dBm  
                Encryption key:on
                ESSID:"MyNetwork"
                Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
                          9 Mb/s; 12 Mb/s; 18 Mb/s
                Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
                Mode:Master
                Extra:tsf=000002b9d7e3023d
                Extra: Last beacon: 52956ms ago
                IE: Unknown: 000843616D656C776562
                IE: Unknown: 010882848B960C121824
                IE: Unknown: 030108
                IE: Unknown: 2A0100
                IE: Unknown: 2D1A6E1003FF00000000000000000000000000000000000000000000
                IE: IEEE 802.11i/WPA2 Version 1
                    Group Cipher : CCMP
                    Pairwise Ciphers (1) : CCMP
                    Authentication Suites (1) : PSK
                IE: Unknown: 32043048606C
                IE: Unknown: 3D1608070000000000000000000000000000000000000000
                IE: Unknown: DD2A000C42000000011E0000000003662D060000453438443843463239313342000000000000000005028F09
                IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00
                IE: Unknown: DD1E00904C336E1003FF00000000000000000000000000000000000000000000
                IE: Unknown: DD1A00904C3408070000000000000000000000000000000000000000
                IE: WPA Version 1
                    Group Cipher : CCMP
                    Pairwise Ciphers (1) : CCMP
                    Authentication Suites (1) : PSK

Update 3

I've wiped the HDD removing windows and bootmanager and installed CentOS7 - hoping that based on LiveCD it's going to work but it failed with the same result: 30Mbps download speed and 400Mbps upload speed.