@majorlinux Unfortunately, the problem with #Sunbird is that it does not have true #E2EE: they log into your Apple ID on a Mac Mini in a datacenter, and then decrypt and re-encrypt the messages on that Mac. The messages are encrypted in transit, but it is not end-to-end in any manner. This was confirmed in MKBHD's video.
This is kind of disappointing to me, because true E2E encryption is possible, I worked on my #pypush project which implements the #iMessage protocol from scratch (no Mac), #Beeper bought it so hopefully should be available in the future.