The software needs to be tested on all supported platforms. Dependencies often are an issue and different ways how to install them. This is a nightmare sometimes because they only seem to test on Ubuntu and CentOS.
I recommend the following, which is based on the majority of systems users report (Windows excluded for now):
You don’t need human ressources for all of that. Most tests can be automated and it is not necessary to support all platforms. But the major plattforms should be tested don’t you think?
And we, as the community, are happy to help as we already post about bugs and errors.
I think that the above platforms should be tested at least that the software really works and that all dependencies are available and instructions should be given how to install them on those systems.
I help whenever I can but I don’t have as much time as I spend the last weeks on the forum and writing up manual material, this is only temporary.
I think the key issue here is not to test on all platforms, but to clearly outline the dependent packages (and minimum versions) that are needed to install together.