How to get Telegram to show up in Dash

The programs that show up in the Dash, desktop menus etc are there due to .desktop files in /usr/share/applications & ~/.local/share/applications. You can easily make a launcher using a file similar to this in either of the above locations (named telegram.desktop or similar):

[Desktop Entry]
Encoding=UTF-8
Name=Telegram
Exec=/opt/Telegram/Telegram -- %u
Icon=/opt/Telegram/telegram128.png
Type=Application
Categories=Network;
MimeType=x-scheme-handler/tg;

Note that the Exec line should contain the command to launch the app (like the one you used in Terminal) - this can be like telegram, /usr/bin/telegram-cli, /opt/Telegram/Telegram etc.

The Icon line points to the icon to use - this can be telegram (if there is are appropriately named icons in ~/.local/share/icons or /usr/share/applications), or point to a icon file directly. (e.g. /opt/Telegram/telegram128.png.). If you need a icon I have uploaded one here.

If the file does not show, try running one of these commands:

update-desktop-database /usr/share/applications
update-desktop-database ~/.local/share/applications

depending on where you placed the file. A restart of the desktop (or logging out and back in again) may be necessary. A similar process can be done for other applications.

The spec for a .desktop file can be found here: http://standards.freedesktop.org/desktop-entry-spec/latest/

Also you can install Telegram using snap (Ubuntu 18.04):

$ sudo snap install telegram-desktop