FWIW, cedar-14 stack is Ubuntu 14.04 and that's been the base of Deis Workflow (now Hephy Workflow) for years. We've been meaning to upgrade to Heroku-16 stack (and eventually Heroku-18) but our resources are limited too, and we've had to fight other dragons like getting a website together, and figuring out the build system. (Deis Workflow was EOL'ed last year, and Team Hephy is the fork/continuation of development, which we can do because Deis developers were all gracious enough to keep everything OSS.)
So, back to the point, I'm sure you couldn't deploy your app on Heroku if that's your requirement (because cedar-14 is deprecated, and not available for new deployments anymore) but if you seriously wanted to try containerizing it onto Kubernetes, and if you don't have other obstacles to 12-factor design that you're also not prepared to tackle, then Hephy Workflow v2.19.4 might actually work for you.
So, back to the point, I'm sure you couldn't deploy your app on Heroku if that's your requirement (because cedar-14 is deprecated, and not available for new deployments anymore) but if you seriously wanted to try containerizing it onto Kubernetes, and if you don't have other obstacles to 12-factor design that you're also not prepared to tackle, then Hephy Workflow v2.19.4 might actually work for you.
https://teamhephy.com and https://docs.teamhephy.com
I'm sure this probably won't work for you, for reasons you may not have explained, but ... maybe you'd like to look?
I'm not doing a great job selling it, the one redeeming quality I've mentioned is that it runs an outdated stack that you need ;)