Technically yes. Likely they still use Transport Layer Security that will encrypt the messages in transit, but that encryption is controlled by the company, and not the end user. What that means is that your messages are safe from randos in the cafe on the same wifi as you, but if the company wanted to, they could read them. It also means that if messages are subpoenaed then they can hand over the unencrypted messages to the authorities.

I tried looking at their documentation to see what was going on under the hood, but there were a lot of connection errors and dead ends. They seem to be open source, though, so if you are so inclined you can comb through their code to see what kind of encryption they use.

Personally, I’d stay away. It doesn’t seem like something that I could put my trust in.