Could def. get this done with puma and a reverse proxy as is. But, if there was a reason to use passenger (blindly following a guide) and nginx you'd run into this.
I got close to getting a ruby app to work (redmine) but a couple issues blocked me from full support on RC.
1. Needs another extra.d include at the top of nginx.conf in nginx-rc folder at the top of the file before main starts. This is to for the load modual line passenger.so.
2. Because nginx comes from RC's own repository, the nginx module I downloaded using ubuntu's 18.04 repositories was the wrong version and didn't want to take the time to figure it out.
If RC provided a way to support those to requests, this might be helpful for others.