> Not perfect, but multiple legal jurisdictions would have to be subpoenad for Telegram to read your non-secret chats.

Thats not how legal works.

for example if I am an EU based judge and I issue a warrant for getting data from a company in a case related to something important (your values may vary, but lets say its not about parking fines) then if your company wants to continue to operate in the EU, you need to pony up the data, or tell them why your can't comply, rather than won't

Having your data stored with keys that you control isn't an excuse.