Ubuntu: if WLAN is gone after an update and lspci lists no wlan devices

On my ubuntu laptop after an update the WLAN networking was gone. First check was to boot into Windows and check wether the WLAN devices is still working:
The WLAN still worked with Windows, so the worst case (hardware error) did not hit me ;-)

So i switched back to Ubuntu and tried the following:

$ lspci -nnk | grep -iA2 net;
02:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 15)
    Subsystem: Acer Incorporated [ALI] RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [1025:104c]
    Kernel driver in use: r8169
    Kernel modules: r8169

Very strange - the WLAN network adapter was not even listed with lspci!
Another check shows:

$ lshw|grep -iA2 network
WARNUNG: Sie sollten dieses Programm mit Systemverwalterrechten (root) ausführen.
           *-network
                Beschreibung: Ethernet interface
                Produkt: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller

It look like the hardware controller is missing, but the check with Windows explicitly showed, that the WLAN is still ok.

The solution was to run:

apt-get install bcmwl-kernel-source

(After connecting the laptop via ethernet to my router)

Then the commands showed up again with the WLAN adapter:

$ lspci -nnk | grep -iA2 net;
02:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 15)
    Subsystem: Acer Incorporated [ALI] RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [1025:104c]
    Kernel driver in use: r8169
    Kernel modules: r8169
03:00.0 Network controller [0280]: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter [168c:003e] (rev 32)
    Subsystem: Lite-On Communications Inc QCA6174 802.11ac Wireless Network Adapter [11ad:0807]
    Kernel driver in use: ath10k_pci
    Kernel modules: ath10k_pci, wl

$ lshw|grep -iA2 network

WARNUNG: Sie sollten dieses Programm mit Systemverwalterrechten (root) ausführen.

           *-network

                Beschreibung: Ethernet interface

                Produkt: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller

--

           *-network

                Beschreibung: Kabellose Verbindung

                Produkt: QCA6174 802.11ac Wireless Network Adapter

                Hersteller: Qualcomm Atheros

                Physische ID: 0

I found the following with google:
https://ubuntuforums.org/showthread.php?t=1411216

So let's try this:

# apt-mark hold bcmwl-kernel-source
bcmwl-kernel-source auf Halten gesetzt.