What are the best cross-platform FLOSS messengers?

Pidgin isn't the most friendly piece of software to use, the very nature of being a multi-protocol messaging suite leads to some fragmented development issues, but it remains one of the only ways to maintain contact with a large contact list over the increasingly diverse instant messaging ecosystem.

The best messenger there is period. Iv'e used this since the beginning and its better than Messenger, Whatsapp, iMessage, etc. It's so good even Whatsapp started "borrowing" their features.

OpenSource, works on every platform without lags. I can send messahes,files, talk with muy contacta using voip, videocalls

Audio/video and messaging works great With the latest update notifications/requests are working pretty good on multiplatform.

Always is the first in bring user new functionalities. It's ability to work simultaneously in distinct platforms and environments make it a productive tool, flexible and always working.

Riot has been absolutely lovely for secure group communication, and the recent addition of voice and video has made it my go-to chatting app on desktop and mobile.

Broken encryption and a lack of features left me wanting more and ultimately looking elsewhere.

So few of us have the deep knowledge of cryptography necessary to gauge when our communications are secure, we have no choice but to select the best such arbiters we can. Signal is the consensus pick of the Electronic Frontier Foundation and Edward Snowden, among others, and so this is where I hang my hat.

Ring

Signal is okay on the surface. It's not too hard to use and works pretty well. However, closed-source server software and a centralized server network make for a pretty weak secure messaging service. At least it's not as bad as Telegram, I suppose.