Just wanted to follow up in a separate thread that the DisplayPort adapter works, and I'm able to use XFCE Terminal with various command line goodies (git, ssh, vim) on an external display.
Next up: exploring alternate browsers in Libertine, perhaps cracking open a compile/build for Firefox, and looking for a Riot.im native app.
Thanks to @advocatux and the rest for help.
@advocatux I'm not in front of the Macbook right now, but I'll see what the logs say when I am, and I'll post here.
Just wanted to follow up in a separate thread that the DisplayPort adapter works, and I'm able to use XFCE Terminal with various command line goodies (git, ssh, vim) on an external display.
Next up: exploring alternate browsers in Libertine, perhaps cracking open a compile/build for Firefox, and looking for a Riot.im native app.
Thanks to @advocatux and the rest for help.
@Lakotaubp Bluetooth mouse and keyboard work without incident. Using the Logitech M535 mouse and the Anker A7721 keyboard. The monitor I have at work is DVI only. I have a DVI to HDMI adapter and I'm using the "MyDP Slimport to HDMI Adapter", but not having much luck. I'll try with my monitor at home, which does have native HDMI and DisplayPort.
As far as Libertine goes, I've installed gnome-calculator as a test; that works. Firefox and Thunderbird, though, don't work. From looking at the Github issues, this seems like it's a known issue.
@advocatux Any thoughts on getting Firefox to work in Libertine?
@advocatux Sure. But, since the output wasn't too egregious and - if some poor soul runs into the same kind of issues I have encountered - then the resulting index in DuckDuckGo or Google can help them in a single thread.
Next up: Libertine containers and running Firefox and a terminal. Bluetooth keyboard and mouse are ordered.
So, the work-around I mentioned above actually works. After trying the SNAP UBPorts Installer on my Debian Sid box, and essentially getting the same results as the macOS counterpart, I decided to try this:
wls@rivendell:~/Downloads$ sudo /usr/bin/ubuntu-device-flash --server=http://system-image.ubports.com touch --device=hammerhead --channel=ubports-touch/16.04/stable --bootstrap --wipe
2018/10/12 20:24:03 Device is |hammerhead|
2018/10/12 20:24:04 Flashing version 3 from ubports-touch/16.04/stable channel and server http://system-image.ubports.com to device hammerhead
56.60 MB / 56.60 MB [====================================================================================================================================================] 100.00 % 8.42 MB/s
378.89 MB / 378.89 MB [==================================================================================================================================================] 100.00 % 7.45 MB/s
/root/.cache/ubuntuimages/ubports-touch/16.04/stable/hammerhead/version-3.tar.xz
/root/.cache/ubuntuimages/gpg/image-master.tar.xz
/root/.cache/ubuntuimages/pool/keyring-4c4e7ef380ebcfa2c31084efa199138e93bfed8fc58aa3eb06bdf75a78af9b57.tar.xz
/root/.cache/ubuntuimages/gpg/image-signing.tar.xz
/root/.cache/ubuntuimages/pool/device-964a84f55b03eca87dacd34dffc9c61c4b50ae471c6b675eafdc2a2eacfad29c.tar.xz
2018/10/12 20:25:15 Start pushing /root/.cache/ubuntuimages/ubports-touch/16.04/stable/hammerhead/version-3.tar.xz to device
2018/10/12 20:25:15 Start pushing /root/.cache/ubuntuimages/gpg/image-master.tar.xz to device
2018/10/12 20:25:15 Start pushing /root/.cache/ubuntuimages/pool/keyring-4c4e7ef380ebcfa2c31084efa199138e93bfed8fc58aa3eb06bdf75a78af9b57.tar.xz to device
2018/10/12 20:25:15 Start pushing /root/.cache/ubuntuimages/gpg/image-signing.tar.xz to device
2018/10/12 20:25:15 Start pushing /root/.cache/ubuntuimages/pool/device-964a84f55b03eca87dacd34dffc9c61c4b50ae471c6b675eafdc2a2eacfad29c.tar.xz to device
2018/10/12 20:25:15 Start pushing /root/.cache/ubuntuimages/pool/ubports-1e002fd7e685421651a9b8dc15b0147c4460993169acd0519183533f17331c84.tar.xz to device
2018/10/12 20:25:15 Done pushing /root/.cache/ubuntuimages/gpg/image-master.tar.xz to device
2018/10/12 20:25:15 Done pushing /root/.cache/ubuntuimages/ubports-touch/16.04/stable/hammerhead/version-3.tar.xz to device
2018/10/12 20:25:15 Done pushing /root/.cache/ubuntuimages/pool/keyring-4c4e7ef380ebcfa2c31084efa199138e93bfed8fc58aa3eb06bdf75a78af9b57.tar.xz to device
2018/10/12 20:25:15 Done pushing /root/.cache/ubuntuimages/gpg/image-signing.tar.xz to device
2018/10/12 20:25:32 Done pushing /root/.cache/ubuntuimages/pool/device-964a84f55b03eca87dacd34dffc9c61c4b50ae471c6b675eafdc2a2eacfad29c.tar.xz to device
2018/10/12 20:26:22 Done pushing /root/.cache/ubuntuimages/pool/ubports-1e002fd7e685421651a9b8dc15b0147c4460993169acd0519183533f17331c84.tar.xz to device
2018/10/12 20:26:22 Created ubuntu_command: /root/.cache/ubuntuimages/ubuntu_commands901896083
2018/10/12 20:26:22 Rebooting into recovery to flash
And Success! I was able to successfully install 16.04/stable onto my old Nexus 5.
Also, to note, while UBPorts Installer is waiting, I can fire up a terminal and run the following:
gondor:~ wls$ fastboot devices
093f6271006d0ccd fastboot
It's also worth noting that the "Report a Bug" button on the installer, at least on my Macbook, doesn't do anything you'd expect - like, open a webpage to report a bug.
@advocatux Here's the output from a terminal from macOS 10.13 (High Sierra):
gondor:~ wls$ which adb
/usr/local/bin/adb
gondor:~ wls$ which fastboot
/usr/local/bin/fastboot
gondor:~ wls$ adb devices
List of devices attached
The UBPorts log is under /Users/<username>/Library/Caches/ubports/ubports-installer.log
From the log:
{"level":"debug","message":"adb shell: echo 1","timestamp":"2018-10-13T01:03:08.934Z"}
{"message":"Command failed: /var/folders/lj/hr4c1zyx4hq5g3hxkhv3vm6m0000gn/T/.com.ubports.installer.K7e0Ud -P 5038 shell echo 1\nerror: no devices/emulators found\n","stack":"Error: Command failed: /var/folders/lj/hr4c1zyx4hq5g3hxkhv3vm6m0000gn/T/.com.ubports.installer.K7e0Ud -P 5038 shell echo 1\nerror: no devices/emulators found\n\n at ChildProcess.exithandler (child_process.js:282:12)\n at emitTwo (events.js:125:13)\n at ChildProcess.emit (events.js:213:7)\n at maybeClose (internal/child_process.js:921:16)\n at Socket.stream.socket.on (internal/child_process.js:348:11)\n at emitOne (events.js:115:13)\n at Socket.emit (events.js:210:7)\n at Pipe._handle.close [as _onclose] (net.js:549:12)","killed":false,"code":1,"signal":null,"cmd":"/var/folders/lj/hr4c1zyx4hq5g3hxkhv3vm6m0000gn/T/.com.ubports.installer.K7e0Ud -P 5038 shell echo 1","level":"debug","timestamp":"2018-10-13T01:03:09.051Z"}
{"level":"debug","message":"adb shell: echo 1","timestamp":"2018-10-13T01:03:10.064Z"}
{"level":"debug","message":"","timestamp":"2018-10-13T01:03:10.223Z"}
{"level":"debug","message":"adb shell: getprop ro.product.device","timestamp":"2018-10-13T01:03:10.226Z"}
{"level":"debug","message":"","timestamp":"2018-10-13T01:03:10.406Z"}
{"level":"debug","message":"getprop: hammerhead","timestamp":"2018-10-13T01:03:10.408Z"}
{"level":"debug","message":"adb shell: cat /etc/system-image/channel.ini","timestamp":"2018-10-13T01:03:12.095Z"}
{"level":"debug","message":"","timestamp":"2018-10-13T01:03:12.298Z"}
{"level":"debug","message":"adb shell: echo 1","timestamp":"2018-10-13T01:03:28.076Z"}
{"level":"debug","message":"","timestamp":"2018-10-13T01:03:28.264Z"}
{"level":"debug","message":"reboot to bootloader","timestamp":"2018-10-13T01:03:28.277Z"}
{"level":"debug","message":"","timestamp":"2018-10-13T01:03:28.867Z"}
{"level":"debug","message":"reboot to bootloader [DONE] err:null","timestamp":"2018-10-13T01:03:28.868Z"}
{"level":"debug","message":"checking password","timestamp":"2018-10-13T01:03:33.845Z"}
{"level":"debug","message":"correct password","timestamp":"2018-10-13T01:03:34.969Z"}
{"level":"debug","message":"fastboot: wait for device","timestamp":"2018-10-13T01:03:34.971Z"}
@advocatux Well, I'll certainly try another USB cable - just in case - but, as I pointed out earlier, if it really was the cable, I would think it would've given me grief when I reflashed the Nexus 5 back to the stock Android 6.0.1 from Google, right? Or, for instance, when I flashed LineageOS on it yesterday, right?
@advocatux I'm not in front of the Macbook right now, but I'll see what the logs say when I am, and I'll post here.
@advocatux I've used this same cable to reimage/flash the Nexus 5. The cable works, AFAICT. 
The installer recognizes the Nexus 5. I select my install options, and then the phone reboots to the bootloader. I think that's from calling fastboot to reboot the phone to the bootloader, correct?
Where would I find the UBPorts Installer log for Mac? I'll pull that and see if that explains why it's not working.