No, it's not and you should consider it as a public space. Only your direct messages are private and nobody can read them, not even admins. But messages in all channels are public. Most recent messages are shown on Nomads.com Chat to non-members too.

The reason is that we don't want to create an illusion of privacy in the chat. There's thousands people on the Telegram. Any of those people may have created a script/robot that just logs and saves every message anyone posts anyway. There's no way for us to stop that. Anyone can pay the membership fee and join and within 5 minutes be in the chat and read your messages.

That's why you should consider it as a public space. If you'd like to talk in private, switch to DM or to external chat apps.