Ukrainians are some of the bravest people I know.
To the extent that you can, do not use Telegram. Telegram is owned by a single person. This man is a fucking liar.
Telegram infrastructure is linked to the FSB.
https://www.occrp.org/en/investigation/telegram-the-fsb-and-the-man-in-the-middle
Signal is more secure and owned by a nonprofit. The founder of Signal is a professional cryptographer.
https://en.wikipedia.org/wiki/Moxie_Marlinspike
Signal delivers end-to-end encryption by default and collects almost no data.
No, all my friends are capable of finding each other without having to rely on an app to do it for them.