> being FOSS just in the client side, IMO changes little in comparsion with WhatsApp.

There are efforts implementing mtproto servers that are compatible with the Telegram codebase like telegramd [1] or madelineproto [2] in case you want to host your own server.

But, if decentralization is your main focus (interpreting your statement); you probably want to switch to a Matrix-based client anyways.

[1] https://github.com/nebula-chat/telegramd

[2] https://github.com/danog/MadelineProto

I would love to have my own telegram infrastructure. I will check those projects, thank you!

I like Telegram FOSS because it doesn't rely on google's infrastructure to run. That's good enough for me given I already made the questionable decision to run a chat client with a home-baked security protocol ;)

At least you know what your device is doing. But walled garden is definitely bad.