> Is there a way to test locally that the change I make work?

Not very easily. The planet-venus Debian package will install the blog
aggregator we use. If you can install that and clone the
https://github.com/schemeorg/planet.scheme.org repo, you have all the
software we use to run the Planet. planet.sh is the update script.

We can also try adding it to the blogroll on the scheme.org server, and
I can remove it if you don't like the result. Let me know if you want a
Linux account on the server itself.