As we’ve discussed before, there’s an informal QA playbook over here: https://gist.github.com/conorsch/e7556624df59b2a0f8b81f7c0c4f9b7d that’s useful for testing the release candidate Debian packages. Testing from the develop branch is a big step forward, so thanks for putting in the hard work.
As that QA playbook illustrates, we don’t have a convenient story for overriding core aspects of the config such as apt repo URL and apt repo pubkey. In a future version, if we make those values variables, they can be overridden for targeted testing of develop or RC debs.