@FediThing @rysiek @m @xarvos

Besides Matrix, another decentralized alternative to Signal with no phone number required is Delta Chat (as mentioned by others here like @kkarhan and @andrewg). It won't support all of the same features (but it does support some features which Matrix doesn't provide, like disappearing messages) and it should be easy to sync messages between devices. Downstream Delta Lab supports Telegram stickers.