As background, I am in the process of upgrading a few projects from Jenkins and Gitlab CI based CI to use Tekton. In those projects, it is common to see a Jenkinsfile or .gitlab-ci.yml defining what the pipeline is to run for the project. Those files are then used by the corresponding tool at build time whenever a triggering event occurs (such as a merge/commit/etc). Those files would change over time to accommodate whatever was needed by the repository to perform its build and then committed to the repo like any other kind of work performed. This had the desirable behavior of knowing exactly what the build pipeline looked like at any point in the commit history and aiding build reproducibility if handled carefully/correctly.
The corresponding approach with Tekton appears to suggest that you store the CRD yaml files under a /tekton folder. However, most of the documentation and examples I've seen for Tekton focus on what appears to be a manual process of pushing your CRDs out with kubectl. Once the CRDs have been installed, the EventTrigger is capable of using the defined resources whenever necessary, but what happens when I commit an update to the pipeline.yaml? Is the expectation that a developer manually pushes the updated CRDs with kubectl or is there a way for the EventTrigger to automatically use the ./tekton/pipeline.yaml that is stored in the git repo that sourced the event?
You should treat tekton resources like any other kubernetes resource and manage them the same way.
For it to be updated automatically you need a tool like ArgoCD.