Perhaps to a small extent, but it is still end to end encrypted, your messages are safe. Used with care it’s still very secure, especially compared with the only other multi platform and widely used alternative, which at this point would be standard sms."WhatsApp"? Your privacy abandoned, that's "WhatsApp"!
What is the name of the 3rd party app?
I use watusi on my iPad with the Builds.io signing service. Closest thing to the real version I think with added tweaks but some bugs as well..
How safe is it to use that?