I saw an issue with Fakebook Theme, though I’m not sure if the problem was theme related. When I tried to view a topic from the main topics view, I was put into an edit view in the new composer. This was on mobile (android PWA).
I also think I saw an issue when editing a description within an event, I was seeing some weirdness when I tried to add a link within the description, when I pasted the link it seemed to disappear.
I had enabled it for our users, but sadly decided to disable for now. Looking forward to the Beta version when it’s a little more baked!