/Later.
Nothing has worked, except my original install. I haven't tarried, but at least I can say what happened. I installed Mint-18.1 from dvd and then added Freecad and backed up I then did the following:

1. apt-get update & apt-get upgrade on Mint 18.1 using original sources.list.d/. That introduced a freecad bug.
2. apt-get update & apt-get upgrade on Mint 18.1 using a mix of versions sources.list.d/. All these following produced an X bug.
3.apt-get update & apt-get upgrade on Mint 18.1 using the next M int (18.2) and a matching Ubuntu (Zesty) in sources.list.d/.; produced an X bug.

The X bug was that I was thrown out because X wouldn't start. All the usual hotkeys were grabbed by the host system, Mint was a vm, so I couldn't get a terminal to sort it. After the update but before a reboot, I did things like 'apt-get clean, check, fix-broken' but none of it worked.

I can't install from usb, because virtualbox won't install from usb and before anyone suggests it, I'm not going to reinstall virtualbox, because I still remember how exhausting the last time proved to be. Back on the original install AFRAID to apt-get anything.

A few thoughts:

1. Don't mix software sources! Linux Mint 18 is based on Ubuntu 16.04 'Xenial Xerus' and is utterly incompatible with Ubuntu Zesty repositories.
2. Have you tried using the Mint Update tool (instead of apt-get)?
3. If you have a strong preference for apt-get, have you tried using 'apt-get dist-upgrade' instead of 'apt-get upgrade'?
4. Have you tested the self-contained FreeCAD-0.16.6712.glibc2.17-x86_64.AppImage in your Mint VM guest?
5. Have you tested the self-contained FreeCAD-0.16.6712.glibc2.17-x86_64.AppImage in your Slackware host?

1. I only spotted that this afternoon. Mark Shuttleworth should definitely be committed for his project names alone. No wonder the Ubuntu user here all use version numbers.
2. It's pretty inscrutable to a first time user and it probably just calls apt-get anyhow.
3. I have and Yes.
4. Not yet. Didn't know it was self contained. Is it statically compiled or what?
5. Didn't know they did one that would fit. Slackware uses the /lib(32 bit) & /lib64 format and doesn't have the 256 dependent python modules, each of which requires a slackbuild, a download of source, and a build. That's why Mint went in - to avoid that. I can transmogrify rpms and debs to tar.gz and the process loses dependency info. If It has the python mods, I can explode the targz in a directory, change the directories around to my liking, and make a slackware package of that. But all the fine tuning (e.g. letting python know it now has these modules) doesn't happen.

EDIT: A simple apt-get update && apt-get upgrade pukes; Narrowed that to the kernel. Hanging onto the old one and trying it again.

You can read more about what exactly an "AppImage" is here: https://appimage.org/

I'm somewhat mind-boggled that you're 6 days into this project and haven't yet tried the easy instructions on the FreeCAD site.

It still pukes even keeping the old kernel. The only other file I get a choice on is some desktop 'use this app for that file type' thing, and I doubt if that will bring the house down. When I get dvds, I'll drop 18.1 and go to 18.3. I'm just wasting bandwidth upgrading seeing as I can't get into the hung system.

I added the freecad repository (What a PITA) to my sources.list.d and got an update going. I'll have to try drawing something in it before I know it's good, but they're adding features at a rate of knots and keeping the stable releases stable, so it's probably worth it. Everyone is supposed to religiously update. My problem's gone, but others remain.

It's a pity Qcad is as inscrutable as the sphinx. I drew a complicated file on freecad (in pythyon), 1 long solid with about 45 holes and it took forever to load/redraw.

I honestly have no idea what you are talking about with this six-day "nothing works, everything is broken, it still pukes" rant. The instructions are incredibly easy: Simply download the AppImage, make it executable, and double-click it to launch. No need to edit software sources; no need to update; no need to even use a VM if you don't want to.

I tested it for you on my Mint 18 VM and it definitely works.

As you can see from Post #1 Here I haven't been keeping track of developments. I don't see slackware there anyhow. It's a passing hobby, not a project that I'm spend a small amount of time on.

Here is the direct download link for your convenience: https://github.com/FreeCAD/FreeCAD/r...86_64.AppImage

That has landed in the Slackware system. That will challenge it. Mind you, the 0.16.712 update actually works in a bog standard Mint-18.1 also, much to my surprise. Only the upgrade does not. I suppose I should upgrade everything more often than once every blue moon.

EDIT: As things stand, I don't hugely have either the spare cpu power or redundant space for a lot of sandboxing, although a few such would hardly dent things.

To my surprise, The AppImage Freecad (139 MB) came up and ran in Slackware-14.2 on glibc-2.23. It acts passably as a freecad viewer, loading/saving files, etc.

When I tried to draw something simple (a turner's cube), however, I was assailed by spurious bugs. This turner's cube is a cube with three concentric pockets out of each side, such that the thing ends up nearly hollow. The python implementation is sad. I couldn't complete one side. I ran into trouble doing simple tasks, and will have to stick with mint. It would probably do well for something relying less on outside forces. Freecad is really half-ware. The python modules belong in /usr/lib64/python-<version>/site-packages, and it's fluke if anything else has them. Even if they do, they will hardly be indexed in pkgconfig, so will not be found.

I have to correct this. There is a way to draw the turner's cube in the AppImage, but it's a bit like walking along a narrow ledge without making one mistake. I can only do that because I can now draw a turner's cube in my sleep.

The Appimage is also noticeably slower than the Mint VM, about the same as the Debian one. It's not even as fast as the Debian VM. Once I get Mint-18.3 installed, I can upgrade immediately and weekly after that, and update the backup if it doesn't puke.

EDIT: I drew the 6 sides of a turner's cube. The measurements are: cube of 200 mm; Each side has 3 concentric pockets
Radius 31.25mm x 75mm deep
Radius 62.5mm x 50mm deep
Radius 93.75 x 25mm deep
As you can see, The thing is repeatable. But the Appimage drawing is visibly wrong on one side, although all dimensions are correct - even in another freecad.