I've been using Ardour since 2002. It's certainly grown a lot since then, but has its issues, especially in the UI department. Your comparison to GIMP is a pretty fair one.
There's a good (and cheap!) way around this, though, and that's Harrison Mixbus. It's based on Ardour, but adds a very nice GUI based on Harrison's consoles as well as some of the best compression and tape saturation effects I've used. There are quite a few how-to videos on their website.
The best part is that often - like right now - they run a special where it's only $19 - it's usually $89.
You cannot just copy .so files from LMMS and expect them to work in other DAWs. Standalone ZynAddSubFX VST plugin is sold commercially - or you can build it from the source (which is certainly not easy). If you download the demo VST from here, does it work? http://zynaddsubfx.sourceforge.net/download.html
> When I was looking into GitLab before I didn't notice that the community edition supported LFS so I'll burn that bridge when I come to it.
I'm still getting my text-based documents workflow straightened out, so I haven't yet taken on binary files. I did notice, though, that GitLab (including Community Edition) does purport to support git-lfs.