Everybody is saying a reverse proxy which is correct, but you said docker stacks, so if that means docker compose then the names of your container is also in DNS so you can use that.
Can't remember if port is needed still or not however.
Signal stands for privacy and not selling your data to be spied on and sold, and you're STILL using SMS, spam ridden, high cost, old infrastructure, easily read, technology.
I suppose you want email in your Signal client too?
Everybody is saying a reverse proxy which is correct, but you said docker stacks, so if that means docker compose then the names of your container is also in DNS so you can use that.
Can't remember if port is needed still or not however.