there may be foss clients, but they still connect closed source TG servers, you can't self host TG, it's centralised
if you trust TG you might just as well trust TikTok
or SMS
Just because you've invested time building TG communities and content, doesn't justify shilling TG as a safe platform for chatting / communicating. It's not paranoia, you know as well as I do that TG admins can see a LOT of detail in relation to users and conversations.