It seems you were right, for some reason the newer BIOS was only available from ASUS USA site and not in Finland and the WinFlash was unable to download it. However now it's updated and this bug still exists.
# sudo dmidecode -s bios-version && sudo dmidecode -s bios-release-date X550JX.209 10/31/2015 ** Changed in: linux (Ubuntu) Status: Incomplete => Confirmed -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1528005 Title: rtl8821ae has no connectivity in 5GHz networks Status in linux package in Ubuntu: Confirmed Bug description: I get IP address and everything, but no connectivity. I cannot ping even the router. ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: linux-image-4.3.0-2-generic 4.3.0-2.11 [modified: boot/vmlinuz-4.3.0-2-generic] ProcVersionSignature: Ubuntu 4.3.0-2.11-generic 4.3.0 Uname: Linux 4.3.0-2-generic x86_64 NonfreeKernelModules: nvidia ApportVersion: 2.19.3-0ubuntu2 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: mikaela 1567 F.... pulseaudio /dev/snd/controlC1: mikaela 1567 F.... pulseaudio CurrentDesktop: MATE Date: Sun Dec 20 16:01:13 2015 HibernationDevice: RESUME=UUID=431ec214-73ef-4058-b283-5721bb5a45d2 InstallationDate: Installed on 2015-12-12 (7 days ago) InstallationMedia: Ubuntu-MATE 16.04 LTS "Xenial Xerus" - Alpha amd64 (20151212) Lsusb: Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 003: ID 0bda:57b4 Realtek Semiconductor Corp. Bus 001 Device 006: ID 13d3:3414 IMC Networks Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub MachineType: ASUSTeK COMPUTER INC. X550JX ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.3.0-2-generic.efi.signed root=UUID=ab0e7270-40bc-4a68-a541-59fd96690354 ro rw acpi_osi= RelatedPackageVersions: linux-restricted-modules-4.3.0-2-generic N/A linux-backports-modules-4.3.0-2-generic N/A linux-firmware 1.154 SourcePackage: linux UdevLog: Error: [Errno 2] Tiedostoa tai hakemistoa ei ole: '/var/log/udev' UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 05/07/2015 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: X550JX.204 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: X550JX dmi.board.vendor: ASUSTeK COMPUTER INC. dmi.board.version: 1.0 dmi.chassis.asset.tag: ATN12345678901234567 dmi.chassis.type: 10 dmi.chassis.vendor: ASUSTeK COMPUTER INC. dmi.chassis.version: 1.0 dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrX550JX.204:bd05/07/2015:svnASUSTeKCOMPUTERINC.:pnX550JX:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnX550JX:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0: dmi.product.name: X550JX dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK COMPUTER INC. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1528005/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp