Ah ha! figured it out. But I still think there is a NodeBB issue. a redirect should never do this.
On my forum, i never set config.json to https. it was http://obelisk.daerma.com I changed it to https://obelisk.daerma.com and it works.
I doubt it is my Nginx proxy because that is about as basic as it gets.
Even if I am in a thread and then click login, it happens.
@julian I saw manual for it (but on Russian): https://habrahabr.ru/post/264301/
And did find special service for Telegram login (not tested): https://telegramlogin.com/
I hope Its will help a little bit