Another plausible alternative is that Telegram embeds an open source NLP model in the app so translation can be performed locally (offline).

To be fair we know that mobile hardware resources can be extremely limited, and I’d wager a server side model will always be bigger and therefore better.

But recently there’s been a lot of amazing progress in techniques to shrink large models down while preserving most of the accuracy (eg quantization aware training, etc).

With some additional constraints on scope (maybe only supporting the handful of languages the user needs?), I believe a sharp team of a few experts could deliver this fairly quickly, with reasonable results that would of course improve over time.