原因：
在使用ThinkPad T14s筆記本安裝使用Ubuntu16時，遇到了WiFi無法使用的情況，原因是ThinkPad T14s支持了WiFi6並升級到了最新的網卡 英特爾® Wi-Fi 6 AX201 160MHz。
參考英特爾® 無線適配器的 Linux* 支持：
https://www.intel.cn/content/www/cn/zh/support/articles/000005511/network-and-i-o/wireless-networking.html
可以看到必需要升級kernel版本到5.2以上，Ubuntu16.04 默認的kernel版本應該是4.*，所以首先升級kernel：
打開 http://kernel.ubuntu.com/~kernel-ppa/mainline/ 並選擇列表中需要的版本，下面的例子用的5.2.4，建議使用5.*版本。速度慢的話可以找國內的源。
uanme -sr
wget https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.2.4/linux-headers-5.2.4-050204_5.2.4-050204.201907280731_all.deb
wget https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.2.4/linux-headers-5.2.4-050204-generic_5.2.4-050204.201907280731_amd64.deb
wget https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.2.4/linux-image-unsigned-5.2.4-050204-generic_5.2.4-050204.201907280731_amd64.deb
wget https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.2.4/linux-modules-5.2.4-050204-generic_5.2.4-050204.201907280731_amd64.deb
sudo dpkg -i *.deb
sudo reboot
uanme -sr
解決方案：
官方源：https://git.kernel.org/cgit/linux/kernel/git/firmware/linux-firmware.git
國內源：
https://mirrors.tuna.tsinghua.edu.cn/git/linux-firmware.git
這個鏈接的庫包含了linux需要的最新的各種驅動，當然也包含無線適配器的驅動，下載了複製到 /lib/firmware/下，重啓即可解決。
README
This repository contains all these firmware images which have been
extracted from older drivers, as well various new firmware images
which we were never permitted to include in a GPL’d work, but which we
have been permitted to redistribute under separate cover.
git clone https://mirrors.tuna.tsinghua.edu.cn/git/linux-firmware.git
cd linux-firmware
sudo cp iw* /lib/firmware/
or copy all drivers to /lib/firmware/ :
git clone https://mirrors.tuna.tsinghua.edu.cn/git/linux-firmware.git
sudo cp * /lib/firmware/
sudo reboot