There are 2 repositories under telegram-checker topic.
Source code from Switchblade CC Checker (Telegram) Please remind, there's no more update for this repo.
A telegram username checker
Telegram Prime (ex. Telegram Gods) ENG
Telegram-Gods (быв. Telegram-Soft)
Telegram Prime (быв. Telegram Gods) RUS
The best tool to check the list of phone numbers for cut which have Telegram accounts
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.