I have found several old pieces of software that do the trick for the instances I have needed them, but I was wondering if really no one in the open source community has developed one of these recently.
I am not a developer (although I am learning to code, but only as a hobby for now) and have used those programs only to supply patches to friends and acquaintances for DOS games and other old unsupported software, creating them from diffing the latest versions I have with the older ones they have.
I'm not looking for anything fancy, but the resulting files should be usable by a complete neophyte, ideally being an executable that only needs to be pointed to a directory to do its thing. So, no, the software mentioned in the only other diff patching question I found in this site (here) is not relevant to me.
I have used Patch Maker (by ClickTeam, dated 2015, although the interface tells me it has been quite a longer time since the last overhaul) and PatchWise Free (by Hanmen, apparently defunct). I have also seen mentions and downloads for Inno Setup XDELTA Patch Maker, and the NSIS Patch Generation Utility, both of which seem to be much older than the other two.