Of course the prometheus HTTPs config can't be default server.

roles/service-prometheus/templates/prometheus_nginx.conf.j2

@@ -1,6 +1,6 @@
 server {
-  listen          443 ssl http2 default_server;
-  listen          [::]:443 ssl http2 default_server;
+  listen          443 ssl http2;
+  listen          [::]:443 ssl http2;
   server_name     {{ prometheus_domain }};
 
   include /etc/nginx/ssl.conf;