Signal Private Messenger is free open source, works on everything. Your grandma could use this.
I have slowly migrated all of my friends and family to this over the last few years.
All of the big 'encrypted' messengers like WhatsApp or Facebook Messenger use the Signal Protocol under the hood but insert their own shady business and tracking defeating a lot of the purpose.
There are other perhaps more anonymous options like SimpleX or XMRchat but they are not practical nor needed for most threat models.
Matrix is not quite mature enough but is a better option than discord for gaming communities.
Signal everyday. I would not recommend Telegram. DYOR.
Sir, this is a Wendy's.