So if the official instructions don’t enable you to get the UCL VPN service working with the official Cisco client then you should try the following

The Pango Library is required by the client software, not having this generally prevents the software from launching without an obvious error

I’ve tried the following with the 64bit version of the AnyConnect client version 4.8.01090 or above on Ubuntu 20.04 LTS

you can enter the following command into Terminal to ensure you have the Pango Library installed

Ubuntu 20.04

sudo apt install libgtk2.0-0 libpangox-1.0-0

Install the library and then follow the guidelines in the UCL Setup guide, that’s all that’s needed - for reference - UCL VPN Guide