Fuck Signal. SimpleX is the best.
Discussion
Simplex require your phone to be on the same network as your computer to work on desktop. This make simplex annoying to use.
I figured out a solution to this "problem" a long time ago (before LAN sync even existed).
I have two accounts, SimpleX-Linux and SimpleX-GrapheneOS. For each contact, I create a chat where I add my two device accounts, and the person I'm chatting with does the same.
I name the chats in this format: "Russell<->TheFuzzStone", and I don't need to sync via LAN.
Simple and it works. :)