I've been to a lot of meetups in the last year and exchanged contacts with people. As a nerdy idealist running a deGoogled Android with no proprietary software, I always have to tell them that I don’t have WhatsApp, just Signal. Again and again I have heard the reply, “Oh, yeah, I’ve got Signal, I use it to buy drugs.”
So, that’s some of the active user base in my city, but none of those users are very motivated to use Signal with their network of contacts in general. There WhatsApp reigns.