Tox has been on my radar for quite some time now. The chance for me to try it finally came up. At first, I was confused trying to self-host a server that I thought was needed only to find out that it is a peer-to-peer protocol without the need for any central servers. That was a big hint that I was onto something not only privacy respecting but also possibly unstoppable by a dictatorship. I am the resident of a country that had an actual dictatorship when I was born, so a sudden twist of events in political status is not science fiction to me.
There are quite a few implementations of this protocol running on various free and open-source chat clients and I chose to go with qTox since it was the official one that also happened to have an AppImage for Linux available.
On Android the simple yet effective aTox, that is also available on F-Droid, was my choice. It seems to have the most current development activity. Although it's missing a lot features it has basic chat functionality along with file transfers.
If you are looking for chat groups you can find them on the desktop applications, the mobile ones are still lacking behind, but they are truly free as in both freedom and money. Not having a laundry list of permissions just to chat with friends and family should be the standard, yet we have to rely on community initiatives like Tox in order to fulfil that space.
Tox client implementations are not your GIF searching, meme inducing run-of-the-mill spyware that we have become so accustomed to, they get the job done and that is it. If privacy is what you are after you should try them, if not you can always pick the ones your friends are on...