Would it work for users without profile pic, by the

way?

that's the point: getChat would not. You cannot rely on it in that cases

i've came up with idea to store info if user had a pfp on his first start. So if the profile pic gets deleted - you probably got banned. PROBABLY. That's the problem. Well if you are checking permission only in private chats you can just rely on https://core.telegram.org/method/users.getFullUser. Check the status of him

But I am clueless on users without pfp from the start, that's the bigger problem. I don't really thing a lot of people delete pfp "casually". What do you think about silent message try?

I have a userbot with "!ignore" function in it. It deletes all incoming messages from anybody in ignore list. Just a way to blacklist somebody without loosing my ability to write to him And even since messages are being deleted INSTANTLY after I receive them, telegram still sends a notification that won't disappear. So that's a risky way

Again, for private chats getting user online status should be enough

You didn't mention that, I guess. Private chats are what I need now. Would try this one.