This Git repo can work :
This is a follow up to stason‘s answer who suggests using dkms.
As far as I can tell, at the time of writing this, there is not yet a Wifi Driver for the Realtek RTL8821CE in the official Ubuntu Repositories.
Over on github there is a repository with an RTL8821CE driver aimed at kernels 4.14 and above and specifically for Arch Linux with no support provided for other Linux Distros: https://github.com/tomaspinho/rtl8821ce
(Minor note: as of February 2019 tomaspinho is sadly no longer able to maintain the driver as he no longer has access to a computer with this chipset, and so a new maintainer may be needed, but the driver still works with Ubuntu 18.04 as at that time.)
It has, however, been reported to work just fine with Ubuntu 18.04.
A temporary internet connection will be required (such as an ethernet cable, USB wifi dongleor connecting your phone with a usb cable and ‘tethering‘ it to use your phone’s Wifi)
The solution is taken directly from post #4 by Praseodym (much praise to their wisdom!): https://ubuntuforums.org/showthread.php?t=2398917 and will install a number of packages for building the wifi driver module (git, dkms, build-essential & linux-headers) and clone the rtl8821ce git repository from tomaspinho (much praise also!).
DKMS is used because it’s “a system which will automatically recompile and install a kernel module when a new kernel gets installed or updated.”
Open up a terminal and type the following lines (You can cut and paste if you prefer):
sudo apt-get install --reinstall git dkms build-essential linux-headers-$(uname -r) git clone https://github.com/tomaspinho/rtl8821ce cd rtl8821ce chmod +x dkms-install.sh chmod +x dkms-remove.sh sudo ./dkms-install.sh
After this is completed successfully, you should reboot and find that your Wifi is working.
You also want to make sure SecureBoot is Disabled in the BIOS settings or it won’t let you load the unsigned self-complied kernel module.