Would be nice to see the Kubernetes versions that retool is known to support. Right now, I cross my fingers with each upgrade on the Kubernetes side.
Hey @joshua.m.pritchard - welcome back to the forum!
I can see why it would be nice to have a little more info about version compatibility. The "hold your breath" strategy only works until it doesn't. 
We don't currently publish any compatibility charts, but I can point you towards a few different resource in order to give you a little more peace-of-mind when upgrading.
Are you deploying with Retool's template manifests? With or without temporal? If so, none of the specified resources should have any version dependency.
It doesn't sound like you're deploying with Helm but I'll go ahead and throw this out there, as well. It documents permitted version skew between your Kubernetes cluster and Helm client.
Last but not least, kubent is a great command-line tool that evaluates your cluster and alerts you if a current resource is using an API that will be deprecated in a future Kubernetes version. You should be able to catch any breaking changes by running this before upgrading!