So I think I understand the workflow on how #TeamJorge is able to hijack Telegram accounts. They need help from the local telecom authority to intercept SMS but! When you register the same phone number on a different device, you first get a push notification inside Telegram..
However, below you can also click, send me an SMS code. This is bad if you don't have 2FA setup with an additional password on Telegram! As #TeamJorge is able to hijack your Telegram account this way!
Always remember to setup 2-factor authentication on all your messengers!
This is how to on Telegram: https://businessinsider.com/guides/tech/enable-two-step-verification-on-telegram
This is how to on Whatsapp: https://faq.whatsapp.com/1920866721452534
This is how to on Signal: https://support.signal.org/hc/en-us/articles/360007059792-Signal-PIN
It's a very noisy attack, you get notifications on your SMS app as your messenger app with codes. But it seems to work for the attackers!
IMHO, all the messengers should force a 2nd-factor on registration for which you need to provide periodic reminders ala Signal. This should keep attackers out that are able to hijack through SS7/telco layers.