Is it possible to use helm post render with fleet?

I have several 3rd party helm charts which force using secrets within their helm values, not allowing any other option to install them otherwise.

While I can fork and fix them to my own needs, I thought that using helm post-render option would be easier to use, that way I could just override their requirements with an ExternalSecret setup.

With one of these charts I tried installing the ExternalSecret along side the 3rd party chart, while using a dummy value for the required secret within the values.yaml. The problem with that is that the running pod contains an environment variable with the dummy value instead of the overridden value coming from the ExternalSecret.