I mean, I could, but I think it's fair for me to assume that the GitHub repository that the official website links to as the source code for their client is where they’d publish up-to-date code.
They might well publish it right there if you ask. Just saying they haven't violated the license as long as they have a written offer to provide you with the source code somehow if you ask. (That's what GPLv2 seems to require.)
They provide no alternative "written offer". On the website, they directly point to GitHub for the source code offer: https://telegram.org/apps#source-code
