Linux Shout published a tutorial about installing the Telegram Desktop App on Ubuntu 20.04 LTS.
How to install Telegram Desktop App on Ubuntu 20.04 LTS
Install telegram linux desktop app for Ubuntu 20.04 LTS oe 18.04, CentOS, Linux Mint, Kali Linux, Debian 10 along with Desktop shortcut.
How to install Telegram Desktop App on Ubuntu 20.04 LTS - Linux Shout