chatty 0.6.0-1pureos2 is now in byzantium for sure. You might have hit a bug where package lists don’t get updated for some (yet unknown) reason - try sudo rm /var/lib/apt/lists/* and then sudo apt update.
There is nothing in the release notes about new MMS functionality in version 0.6.0, but Chatty 0.5.0.beta3 added support for MMS, so version 0.6.0 should support it as well.
Yes, MMS works, and Chatty now shows images inline nicely instead of just file:// links as it was in some earlier chatty versions.
However, for me there is the problem that a normal incoming MMS that is sent from someone to me (that I would have expected to be part of my SMS conversation with that person) gets handled as part of a “group chat” so it appears as a separate conversation in Chatty. That’s a bit annoying, but the MMS does arrive which is the most important thing.
great news, I have to try this out as this was one must have feature I needed to make this phone my daily driver. I hope they improve how it shows up, but as long as it works, I can deal for now.