Most often use a Telegram but it depends on the country in which you will use this messenger. For example, the management of Telegrams in Russia is now given 15 days to provide their codes for encryption. If they fulfill this condition then the privacy of the network will be reduced to zero. If not then probably Telegrams will be banned in Russia and satellite countries.
That's really interesting... I wonder what impact this will have on a lot of the crypto channels. Most of the big ones seem to be Russian.
I do find Telegram really scammy, it takes a while to get to know the good channels. However, recently people keep talking about Telegram more and more in the context of ICOs. Less so Slack and Discord