A lot of Russian people use Telegram, but a lot of Russian people are also using Whatsapp. Me personally, I use Skype/Whatsapp strictly for work and Discord for everything else. I have severe gripes with Whatsapp including a sub-standard desktop client. Signal is a pretty good replacement for Whatsapp I would say. We have recently been approved at work to start using a corporate version of Zoom but it is seldom used yet. We also heavily use Symphony at this point for group conversations that don't involve voice calling. I think LINE and Telegram are pretty ok. IRC is still always gonna be my favorite but obviously its lacking most of the features of a modern chat client such as Discord such as video/audio calls and screen-sharing.