As I stated in the addendum to the introduction, the primary purpose of the AV computer is to record & edit our services. Probably the most widely known FLOSS audio editor is Audacity. I don't know when I was introduced to it, but I think it was early on in my teen years when my oldest brother used it to edit services for our church (different than the church I am now at). As such I am quite familiar with Audacity and never really though twice about using it. However, there are a plethora of other audio editor options! I'll discuss some of them, starting with Audacity.
Audacity may not be the most feature rich editor available but it certainly has far more than enough for any task I've ever asked it to do. The main interface is simple (compared to many editors), listing the playback and record buttons, a small selection of mouse tools, input and output levels, basic editing tools (such as copy, past, trim, and zoom), and input options at the top with most of the interface taken up by the audio track display. There is a toolbar at the bottom, but I have never had need for it.
The menu bar has many other options and tools available for use. The options I primarily use are amplify, noise removal, generate silence, edit metadata and export. The version of Audacity available in the Ubuntu 16.04 repositories has a small bug where the export menu will automatically append .aiff to any export no matter the format selected. This has been fixed in later version of Audacity but has not been backported in the Ubuntu repos. The latest version of Audacity can however be used on older versions of Ubuntu by adding the Audacity PPA. Audacity is licensed primarily under the GPL v2 but has some components under other licenses. Many plugins are also available for Audacity.
Ardour is a fully featured DAW and therefore far more powerful than necessary for my AV tasks. Ardour is licensed under the GPL v2 but does charge for pre-built binaries. Linux users can often simply install Ardour through their distros' repositories.
I have never used a true DAW and so can't say much about the usability of Ardour. I installed it (a simple "apt install" works on Ubuntu flavors) and fired it up but the interface seemed to be locked up (I likely configured something incorrectly in the launch walk-through). Since I didn't know what I was doing anyway, I then uninstalled it.
Ocenaudio seems to be more focused on editing than recording, though it offers that too. At first glance, the most obvious thing is the logo; it's literally a screaming (singing?) head wearing headphones. Builds are offered for free for most platforms (oddly, the debian 9 package didn't work on my personal Kubuntu 17.10 machine but the debian 8 package does). I don't know how it is licensed or even if it is FLOSS as there is nothing about it mentioned on their website and apparently no link to source.
The interface is lovably simple with record, play, jump to beginning, rewind, fast-forward, and properties buttons being the only major UI buttons. KDE users will be happy to know that ocenaudio is built with Qt framework so it looks right at home on Plasma. Unlike the somewhat stark look of Audacity, ocenaudio's color theme is almost eye candy with the audio waveforms a nicely muted mint green, backgrounds a dark blue-grey, and touches of orange and red. There is a really nice sidebar that allows you to load multiple files or recordings (what Audacity would call projects) into the program at once but still work on each individually. A navigator at the top of the editing frame allows you to easily move around in the track without loosing your current selection. The total options are more limited than what Audacity offers but seem to be more than adequate for simple sermon/service editing. Overall, I really like ocenaudio.
Kwave (licensed under GPL v2) is an editor built with the KDE framework so it ought to look even more at home in Plasma than ocenaudio. Unfortunately, it doesn't; the interface, while not terrible, does look like many early KDE applications with a lack of cohesive button design and bad color choices. Waveforms are displayed white on black until you try selecting a portion at which point you get treated to blue on yellow. Playback is also lackluster with several second hangs when you start or stop. Editing options offered are the bare minimum.
The only positives I can offer about Kwave are that it does provide tabs for opening multiple files/recordings and it also includes a navigator for easy movement within tracks. With the last update released in 2016 and usability issues, Kwave appears to be a dying project.
There are many other audio editors available; I'll list several of them here.
Traverso-DAW - a no-frills DAW recently ported to Qt
EKO - "a simple sound editor"
rezound - a Linux first editor
Harrison Mixbus - a commercial DAW that attempts to mimic a hardware mixer
Ecasound - a command-line audio editor (because no list of Linux software is complete without a command-line option, right?)