Spoiler: I'm the OpenFaaS Founder, so am biased here. This is probably our best tutorial so far on automating OpenFaaS installation and function updates using Argo CD. We've had previous articles, but I'd say this is the most concise and also the only one to cover the Image Updater. Argo's Image Updater watches a container registry and updates your Helm chart's YAML files automatically.
You can apply what we've covered for your own CRDs or Kubernetes objects, so feel free to take a peak even if you're not an OpenFaaS user yet.