Is there any write-up about interops between any of them?

Of course, imho, being aware of your own lack of knowledge is something already.

isn’t that another way of calling ignorance aka being dumb?

Isn’t that what Lineage does?

The last one which I tried yesterday, was forcing window decoration on window.

That’s disappointing…

What isn’t? Most of it doesn’t work under Wayland.

What’s the point of Goggle’s security support when you’re buying the phone for GrapheneOS?

The aim of Signal Foundation is to displace the likes of WhatsApp and Messenger thus it has to support all modern and expected features.
Interestingly enough WhatsApp uses Signal’s protocol for encryption, it’s part of the planned messaging interop forced on Meta by EU.

Molly allows you to use alternative push servers (instead of Google’s), amongst other things.

What exactly is there to port anyway?

Gorgeous. I need someone to pick up Cantata.