https://help.twitter.com/en/managing-your-account/twitter-username-rules
https://www.facebook.com/help/1740158369563165
https://www.linkedin.com/help/linkedin/answer/a522735/find-your-linkedin-public-profile-url?lang=en
https://www.facebook.com/help/instagram/369207764224422
Telegram
To create a Telegram username, head over to the hamburger menu located at the top right corner of the app's home screen and tap on 'Settings.' In the menu, the section titled 'Account' will contain an option that reads 'Username.' Tap on it.
On the following screen, Telegram mentions that "people will be able to find you by this username and contact you without needing your phone number." As users start creating their username and add characters to it, the application also tells whether the combination is available or not. Once users have created the desired username, they should tap on the tick icon at the top right corner.
While you are allowed to change your username after setting it, do note that you will need to update the telegram username on the digital name card.
Add your username with "t.me/", example, if your username is "AstuteAdviser", then you will need to input "t.me/AstuteAdviser".