Every linux package has a maintainer. But what does he do ? what is his job ? does he simply compile a new version of the software each time a new version is released by the original authors ? is he responsible for testing the software for that distribution ? does he make some changes to the original source code to adapt the package to the distro’s peculiarities (installing files in different folders) ? what specific skills does one has to have to be a package maintainer ? does he have to be a master of config and make for the most part ? what's the toolchain like ? what does one has to learn to be a good package maintainer ?

If you are a package maintainer and would like so share your experience that would be much appreciated.

what do you expect now? What is the goal of this thread?
A package maintainer usually maintains one or more packages. Usually that means he/she maintains [all or partially] the source code, package builder, installer, bugs, features and other related things (like documentation). Depends on the complexity of the software and a lot of other things.

Goal of the thread is to learn about what package maintenance is, and how to become one.

Maintaining source code : what does that mean ? what does that involve ? for example : compiling and reporting compile errors/warnings if any to the original authors ? trying to fix them then report ?

Maintaining package builder : this should mean changing the package specifications accordingly (new url, update version number and the like ?)

Maintaining the installer : what is an installer ?

I think there are two kinds of people who could be considered as package maintainers. First there are those who maintain the original source code package, for example something like firefox. Such a package will consist of source files, icons, documentation, etc. and also standard build tools such as Makefiles. The idea is that a user can download the package and install it on his/her machine. Maintenance will consist of fixing bugs and adding functionality. Periodically a new version will be issued.

Another kind of maintainer works on the team of a Linux distribution. These people are responsible for configuring the package build so that it fits smoothly into the distribution. Usually it will be distributed as a collection of binary files together with documentation and accessory files such as icons or fonts. In some distros, source packages are distributed instead, but they come with ready-made build scripts created by the maintainers. Mostly the distro maintainers don't alter the source code but small patches may be necessary in some cases.

Sometimes its quite mundane and simply keeping an eye on source code .have a look at
https://slackbuilds.org and see if there was a package for latex2html for slackware 13.37, 14.0 and 14.1
you won't find any.

Basically the maintainer was not keeping up.

All i did was note that there was a recent 2019 release for source code for latex2html ; sit down at a keyboard and just as Robert Wilensky predicted produce a working slackbuild script. So @Hazel i must fit into your 3rd type of person ?

Different distro have different specifics about what is involved in being a package maintainer.
Debian has the New Maintainers' Guide for their "DebianDevelopers."
Fedora has a set of pages about joining the package collection maintainers.
Arch lists their types of contributors.
I'm sure there are as many methods of organizing the contributors as there are distros.

if you want to become a package maintainer:
1. you need to choose a software (like libreoffice, vi, networkmanager, whatever you prefer).
2. need to be really familiar with it (= usage)
3. probably you can find bugs and also you can have improvement ideas
4. later you can try to fix bugs or implement some features yourself (or in a group)
5. you can decide if a reported bug is really a bug or a requested feature is really valuable enough to put into the software
6. you can build/deliver this software for several different distributions (like ubuntu/suse/redhat/slack ...)
7. be an official maintainer

Obviously it is not the ultimate way, there can be different steps/routes, but the approach should be something like this.

There's no such thing as a Linux package - well, except for the kernel itself maybe.
Packages are distro-specific and so is maintaining them.
There are Ubuntu packages, Debian packages, Fedora packages etc. but no "Linux packages".
Go to a distro of your choice and ask them what it's all about.

That's not quite true. Source packages aren't usually written for any particular distro. It's the binary packages that are distro-specific. But a source package can still do with a maintainer.

Really, apart from distro's that have their own package file format, there is really only Debian packages (*.deb), and RPM packages (*.rpm). So saying a "Fedora package" is a little misleading, given that Fedora like many other distro's use the RPM package format which originally comes from Red Hat (Red Hat Package Manager). So really "Ubuntu packages" are just Debian packages built for Ubuntu rather than Debian itself, and similarly "Fedora packages" are really just RPM packages built for Fedora instead of RHEL itself (or whatever else).

And obviously, contain software compiled for the library versions said distro has. So you would break your system by mixing packages built for Debian with packages built for Ubuntu - even though both distro's use the same package format.

And that's not quite true either. Quite a few distros have their own package format. Deb and RPM are just the commonest ones.

You should read my comment again - as I did say "apart from distro's that have their own package format". You even quoted it.

Oh dear! I really should read more carefully, shouldn't I.
Sorry!

Just for interest, how far is a source packages Linux-specific? I mean, quite a lot of Linux software is used on BSD as well. Does someone have to patch the programs to run on the different OS or is it just a matter of compiling them in that environment?

You're forgiven Hazel

I assume if it's not using Linux system calls or any other Linux-specific things, and you can compile and build it on one of the BSD's, it's not Linux-specific, otherwise it is. So you couldn't compile and build a certain init system who's name we shall not mention (*yst*md) on one of the BSD's because it uses Linux kernel interfaces that aren't available on the BSD's, therefore it is an example of something that's Linux-specific.

So what about C-library calls? Linux uses GNU libc; the BSD's have their own versions. Would that make a difference?