There are 2 repositories under telegram-checker topic.
A telegram username checker
Source code from Switchblade CC Checker (Telegram) Please remind, there's no more update for this repo.
Telegram Prime (ex. Telegram Gods) ENG
Telegram Prime (быв. Telegram Gods) RUS
The best tool to check the list of phone numbers for cut which have Telegram accounts
Telegram-Gods (быв. Telegram-Soft)
Telegram-Gods (ex. Telegram-Soft)
Package for checking parameters of Telegram Web Apps startup. The code is taken from the official documentation and put into one package for easy use.
framgent.com (telegram) usernames checker
Telegram Database Checker is a tool designed to check if a specific phone number is registered on Telegram or Not.