This post addresses two of the tasks that I outlined as important for the A/V system to be able to accomplish; showing presentations of some kind and reading/editing documents. It will not cover everything I want to say on showing presentations as I want to write a dedicated post for that. (Happily, there are several software options that tackle not just presentations, but specifically church presentations. But more on that later.)
The first name that likely comes to your mind when discussing a FLOSS office suite is either Apache OpenOffice or LibreOffice; but which one is better? Unfortunately, this is a question that does need to be answered since it is not recommended to have both installed at the same time. To understate the matter, there are a lot of opinions on both sides of the debate.
My opinion on the matter is that, for our setup, LibreOffice is the better choice. First, LibreOffice is the default office suite on Ubuntu (and most GNU/Linux distros). Second, it has more polish (my opinion). Third (there are more reasons, but I'm trying to keep this somewhat short), LibreOffice receives many more updates, improving its features and compatibility. (Side note: if you prefer to always have the latest update to LibreOffice, add the official PPA.) So I initially decided that LibreOffice was the ideal option for us. It works great. Until someone gives you a PowerPoint file with embedded audio or certain animations in it. Then it falls on its face. Apparently, there are occasional compatibility problems with .docx and .xlsx files too but we've not really had any issues there. OpenOffice doesn't appear to be any better in these areas either.
So we need a GNU/Linux compatible PowerPoint alternative that can play audio and doesn't get tripped up by the PowerPoint animations. There are several other options.
OnlyOffice is a nice, Free/Libre program that offers a desktop option (it is largely online focused). Annoyingly, it does not include a presenter mode but we can live without that. It does seem to work properly with animations but it doesn't have any audio options for presentations at all. There may be a plugin that offers this, but I have not been able to find any.
FreeOffice is a free (not Libre) program that is (feature wise) very similar to OnlyOffice. It doesn't have a presenter view and again it can't play audio (under GNU/Linux) but does work well otherwise. Unlike OnlyOffice, it is at least aware of embedded audio files. FreeOffice is a slightly gimped version of SoftMaker Office so maybe we'll find what we need there.
First, SoftMaker is a German software company that sells (among other things) an office suite for Linux! SoftMaker Office is essentially the same as FreeOffice but with more features and a modest price tag. I tested it out with the nice 30-day trial. It is just as good as FreeOffice at displaying .pptx files and it does include a presenter view! So far so good. Unfortunately, it also shares FreeOffice's lack of audio support under GNU/Linux. This feature is "on the wish list", but until it is implemented, SoftMaker Office is only marginally better than LibreOffice for our needs.
WPS Office is developed by KingSoft, a Chinese software company. While there is no longer official support for GNU/Linux, there is a free (not Libre), community supported version! Unfortunately, it hasn't seen an update since mid-2017 but it should still work, right? Well, it does work on Ubuntu 16.04 (what we are currently running). And it works quite well! Both audio and animations are (apparently) fully supported in PowerPoint files and I have yet to find anything that it fails at.
But (why does there have to be a but?), remember that I said WPS for GNU/Linux hasn't been updated for about a year? Well, that means that under Ubuntu 18.04, one of its dependencies is missing. While there are tutorials to fix this, I haven't had been able to successfully install WPS on my 18.04 system. Further, there are no indications that there are going to be any more updates to WPS for Linux. As I plan to update our A/V machine in the near future to something based on 18.04 (probably LinuxMint 19), I am uncertain if WPS is going to continue to work for us.
Yes, MS Office is actually an option under GNU/Linux because of the nice folks over at CodeWeavers and their CrossOver Linux product. MS Office 2010, 2013, & 2016 are all supported to some extent, with PowerPoint receiving a 4/5 star compatibility rating for all three versions. Unfortunately, Office 2016 Home & Student, is not cheap. It is currently listed at $150. Additionally, you have to purchase CrossOver to get things running (or adventure out on your own with WINE). Especially as PowerPoint only scores 4/5 stars, I am very hesitant to try this.
LibreOffice works for most of our needs. And for the moment, WPS Office is our best option when LibreOffice chokes on a file. It works and works well. For the future, if SoftMaker Office can add audio support, it will probably be our go to solution for displaying PowerPoint files.
One further note: All of the above work well enough with MS Office document files. There are likely some differences in level of compatibility, but nothing that we have run across.