In debian I do "apt-get source x", then modify the source code of x, then "dpkg-buildpackage" to build a modified .deb file which I install to get my modified program. This works fine, I did it many times to apply some little fix or change that I want to use locally.
About use cases, "user" vs "developer", I think part of the point of FOSS is to tear down the barrier between those. We are all developers, and we are all users. Developers don't have special powers over users.
@cwebber@octodon.social