C¶Possibly the most well-known unofficial open source implementation outthere by @vysheng,tgl, and its console clienttelegram-cli. Latest developmenthas been moved to BitBucket.
C++¶The newest (and official) library, written from scratch, is calledtdlib and is what the Telegram Xuses. You can find more information in the official documentation,published here.
JavaScript¶@zerobias is working ontelegram-mtproto,a work-in-progress JavaScript library installable vianpm.
Kotlin¶Kotlogram is a Telegramimplementation written in Kotlin (one of theofficiallanguages forAndroid) by@badoualy, currently as a beta–yet working.
PHP¶A PHP implementation is also available thanks to@danog and hisMadelineProto project, witha very nice onlinedocumentation too.
Python¶A fairly new (as of the end of 2017) Telegram library written from theground up in Python by@delivrance and hisPyrogram library.There isn’t really a reason to pick it over Telethon and it’d be kindasad to see you go, but it would be nice to know what you miss from eachother library in either one so both can improve.
Rust¶The grammers library is made bythe same author as Telethon’s! If you arelooking for a Telethon alternative written in Rust, this is a valid option!
Another older, work-in-progress implementation, on Rust is made by@JuanPotato under the fancyname of Vail.