Or for the new crosspost display to be collpased by default.

That’s what Photon and Thunder do and imo, it works pretty well. Especially for posts with like a 10 crossposts, example.

They’re accepting the changes you’re making fine, you can see as such here.

Assuming my suspicion from the other thread is correct (that you’re running this in your house), you need to set up port forwarding between your router and the computer running Yunohost. Specifically ports 80 and 443.