Having sealed sender only with contacts is an anti spam measure

I would rather deal with spam on my own than have a central entity monitor my communications ( as we can't verify if the signals servers aren't running a modified version of the open source release) + turning on sealed sender for me won't allow my messages to reach the other end if sealed sender isn't turned by default on the other end, should I ask every contact to turn it on before starting a chat with them ? that's a bummer for me ! a useless feature if it isn't turned on by default for everybody.

at signal they are working on removing the requirement for phone numbers.

It has been too years since they have announced that and till now its crickets ! and by what I gathered for forums and github It seems they are not getting rid of phone numbers for sign-up (they might still be mandatory ) but you might have the option to add contacts using their usernames (which is better but not what the community has asked for the most ).