原因：
在使用ThinkPad T14s笔记本安装使用Ubuntu16时，遇到了WiFi无法使用的情况，原因是ThinkPad T14s支持了WiFi6并升级到了最新的网卡 英特尔® Wi-Fi 6 AX201 160MHz。
参考英特尔® 无线适配器的 Linux* 支持：
https://www.intel.cn/content/www/cn/zh/support/articles/000005511/network-and-i-o/wireless-networking.html
可以看到必需要升级kernel版本到5.2以上，Ubuntu16.04 默认的kernel版本应该是4.*，所以首先升级kernel：
打开 http://kernel.ubuntu.com/~kernel-ppa/mainline/ 并选择列表中需要的版本，下面的例子用的5.2.4，建议使用5.*版本。速度慢的话可以找国内的源。
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
解决方案：
官方源：https://git.kernel.org/cgit/linux/kernel/git/firmware/linux-firmware.git
国内源：
https://mirrors.tuna.tsinghua.edu.cn/git/linux-firmware.git
这个链接的库包含了linux需要的最新的各种驱动，当然也包含无线适配器的驱动，下载了复制到 /lib/firmware/下，重启即可解决。
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