An update regarding this:

I have been able to get Anbox Applications installed without adb by doing the following:
(I removed most of them from the log to save space on this post, but keep in mind that there were HUNDREDS of "30 53 E Parcel : Reading a NULL string not supported here." errors that came with this install)

$ sudo anbox-tool disable && sudo anbox-tool upgrade && sudo anbox-tool enable

$ sudo mv Downloads/F-Droid.apk anbox-data/data

$ sudo anbox-tool enable && sudo anbox-tool app-install anbox-data/data/F-Droid.apk
Successfully installed anbox-data/data/F-Droid.apk

$ sudo lxc-console -ndefault -P /home/phablet/anbox-data/containers -t0
Connected to tty 0
Type <Ctrl+a q> to exit the console, <Ctrl+a Ctrl+a> to enter Ctrl+a itself

$ cd data/

$ pm install -r F-Droid.apk # using -r since it has already been installed previously, otherwise would not use this option
08-21 18:21:56.778   900   900 D AndroidRuntime: >>>>>> START com.android.internal.os.RuntimeInit uid 2000 <<<<<<
08-21 18:21:56.784   900   900 D AndroidRuntime: CheckJNI is OFF
08-21 18:21:56.879   900   900 W art     : Unknown instruction set features for ARM CPU variant (generic) using conservative defaults
08-21 18:21:56.886   900   900 D ICU     : No timezone override file found: /data/misc/zoneinfo/current/icu/icu_tzdata.dat
08-21 18:21:56.914   900   900 E memtrack: Couldn't load memtrack module (No such file or directory)
08-21 18:21:56.914   900   900 E android.os.Debug: failed to load memtrack module: -2
08-21 18:21:56.915   900   900 I Radio-JNI: register_android_hardware_Radio DONE
08-21 18:21:56.926   900   900 D AndroidRuntime: Calling main entry com.android.commands.pm.Pm
08-21 18:21:56.976    39    39 I         : free_cache(8605919) avail 111367782400
08-21 18:21:57.428   750   761 I art     : CollectorTransition marksweep + semispace GC freed 49(2656B) AllocSpace objects, 0(0B) LOS objects, 24% free, 6MB/8MB, paused 10.538ms total 10.538ms
08-21 18:21:57.468   110   135 I PackageManager.DexOptimizer: Running dexopt (dex2oat) on: /data/app/vmdl1030667680.tmp/base.apk pkg=org.fdroid.fdroid isa=arm vmSafeMode=false debuggable=false target-filter=interpret-only oatDir = /data/app/vmdl1030667680.tmp/oat sharedLibraries=null
08-21 18:21:57.505   911   911 W dex2oat : Unknown instruction set features for ARM CPU variant (generic) using conservative defaults
08-21 18:21:57.505   911   911 I dex2oat : /system/bin/dex2oat --compiler-filter=interpret-only
08-21 18:21:58.873   911   917 W dex2oat : Before Android 4.1, method android.graphics.PorterDuffColorFilter androidx.vectordrawable.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
08-21 18:22:00.547   911   911 I dex2oat : dex2oat took 3.042s (threads: 8) arena alloc=88KB (91000B) java alloc=6MB (6605888B) native alloc=13MB (14395984B) free=3MB (3691952B)
08-21 18:22:00.574   110   124 I ActivityManager: Force stopping org.fdroid.fdroid appid=10050 user=-1: installPackageLI
08-21 18:22:00.646   110   135 I PackageManager: Package org.fdroid.fdroid codePath changed from /data/app/org.fdroid.fdroid-2 to /data/app/org.fdroid.fdroid-1; Retaining data and using new
08-21 18:22:00.647   110   135 W PackageManager: Code path for org.fdroid.fdroid changing from /data/app/org.fdroid.fdroid-2 to /data/app/org.fdroid.fdroid-1
08-21 18:22:00.647   110   135 W PackageManager: Resource path for org.fdroid.fdroid changing from /data/app/org.fdroid.fdroid-2 to /data/app/org.fdroid.fdroid-1
08-21 18:22:00.706   110   135 W PackageManager: Unknown permission android.permission.FOREGROUND_SERVICE in package org.fdroid.fdroid
08-21 18:22:00.767   110   135 I art     : Starting a blocking GC Explicit
08-21 18:22:00.827   110   135 I art     : Explicit concurrent mark sweep GC freed 28532(1615KB) AllocSpace objects, 10(248KB) LOS objects, 19% free, 10MB/12MB, paused 1.003ms total 59.530ms
08-21 18:22:00.846    39    39 E         : Couldn't opendir /data/app/vmdl1030667680.tmp: No such file or directory
Success
08-21 18:22:00.846   110   135 I ActivityManager: Force stopping org.fdroid.fdroid appid=10050 user=0: pkg removed
08-21 18:22:00.856   110   145 I InputReader: Reconfiguring input devices.  changes=0x00000010
08-21 18:22:00.860   110   145 I InputReader: Reconfiguring input devices.  changes=0x00000010
08-21 18:22:00.860   110   400 I BroadcastQueue: Delay finish: com.android.gallery3d/.app.PackagesMonitor
08-21 18:22:00.861   110   145 I InputReader: Reconfiguring input devices.  changes=0x00000010
08-21 18:22:00.868   900   900 I art     : System.exit called, status: 0
08-21 18:22:00.868   900   900 I AndroidRuntime: VM exiting with result code 0.
08-21 18:22:00.871   110   405 I BroadcastQueue: Resuming delayed broadcast
08-21 18:22:00.872   254   254 E PhoneInterfaceManager: [PhoneIntfMgr] getCarrierPackageNamesForIntent: No UICC
08-21 18:22:00.872   254   254 D CarrierSvcBindHelper: No carrier app for: 0
08-21 18:22:00.873   254   254 E PhoneInterfaceManager: [PhoneIntfMgr] getCarrierPackageNamesForIntent: No UICC
08-21 18:22:00.873   254   254 D CarrierSvcBindHelper: No carrier app for: 0
08-21 18:22:00.873   254   254 D CarrierConfigLoader: mHandler: 9 phoneId: 0
08-21 18:22:00.874   792   792 W ContextImpl: Calling a method in the system process without a qualified user: android.app.ContextImpl.startService:1357 android.content.ContextWrapper.startService:613 android.content.ContextWrapper.startService:613 com.android.keychain.KeyChainBroadcastReceiver.onReceive:12 android.app.ActivityThread.handleReceiver:3040 
08-21 18:22:00.877   110   306 I BroadcastQueue: Delay finish: com.android.keychain/.KeyChainBroadcastReceiver
armv7-a-neon:/data $ 08-21 18:22:00.885   110   123 W Searchables: No global search activity found
08-21 18:22:00.886   110   123 W Searchables: No global search activity found
08-21 18:22:00.886   110   405 I BroadcastQueue: Resuming delayed broadcast
08-21 18:22:00.890   110   404 I BroadcastQueue: Delay finish: com.android.musicfx/.Compatibility$Receiver
08-21 18:22:00.895   110   274 I BroadcastQueue: Resuming delayed broadcast
08-21 18:22:00.897   110   122 W BroadcastQueue: Unable to launch app org.fdroid.fdroid/10050 for broadcast Intent { act=android.intent.action.PACKAGE_REMOVED dat=package:org.fdroid.fdroid flg=0x4000010 (has extras) }: process is bad
08-21 18:22:01.503    30    52 E Parcel  : Reading a NULL string not supported here.
08-21 18:22:01.504   427   427 I AnboxAppMgr: Connected to platform service
08-21 18:22:02.043    30    53 E Parcel  : Reading a NULL string not supported here.
08-21 18:22:02.053   110   404 I BroadcastQueue: Delay finish: com.android.gallery3d/.app.PackagesMonitor
08-21 18:22:02.093   110   306 I BroadcastQueue: Resuming delayed broadcast
08-21 18:22:02.098   110   122 I BroadcastQueue: Delay finish: com.android.musicfx/.Compatibility$Receiver
08-21 18:22:02.106   110   412 I BroadcastQueue: Resuming delayed broadcast
08-21 18:22:02.118   110   121 I BroadcastQueue: Delay finish: com.android.musicfx/.Compatibility$Receiver
08-21 18:22:02.123   110   122 I BroadcastQueue: Resuming delayed broadcast

enter
Ctrl+A q

$ sudo reboot

It seems that it installs, and a reboot is performed. Upon coming back online and refreshing the App Drawer, the stock Android apps appear and F-Droid does as well. Apps such as Clock and Contacts (anbox version) open and function, but F-Droid opens to a black screen and never actually launches. Same happened with 'Idle Heroes' (yes, I am one of those losers)

Any insight is appreciated, but nice to get somewhere where at least something technically installs

Edit:
@stanwood
To your point, while I could easily wait for WayDroid to be integrated to UBTouch for the N6P, where is the fun in that when I can tinker now?

@applee

Thank you for the reply and the warm welcome Happy to finally be here, been waiting a long time to get Linux on an Android device

The file was downloaded directly from the N6P web browser, so the file is stored (on UBTouch Device) ~/Downloads/F-Droid.apk

My only confusion is how to actually push that application to be installed, when the device itself does not support adb and is not a standard android device (no APK package manager)

I believe the link you sent does show an alternative method using anbox-tools, so I will give that a try later and will see if that works

Thank you again for your time and welcome

I am incredibly confused here, hoping someone can assist

I have successfully installed Ubuntu Touch on the Nexus 6P and it is wonderful so far!
I am stumped however on how to install .apk files on the Nexus 6P, considering that ADB is NOT supported.

Obviously ADB over USB doesn't work, and I cannot seem to get the ADB remote shell to work.

On the Laptop:

$ adb connect ubuntu-phablet
connected to ubuntu-phablet:5555

$ adb shell
error: device unauthorized.
This adb server's $ADB_VENDOR_KEYS is not set
Try 'adb kill-server' if that seems wrong.
Otherwise check for a confirmation dialog on your device.

A couple hours of research has not assisted in this unfortunately.
Same exact issue occurs when running:

On Ubuntu Touch (N6P)

$ adb connect -H localhost
connected to localhost:5555

$ adb shell
error: device unauthorized.
This adb server's $ADB_VENDOR_KEYS is not set
Try 'adb kill-server' if that seems wrong.
Otherwise check for a confirmation dialog on your device.

If trying to install locally on the N6P:

$ adb install Downloads/F-Droid.apk
error: device unauthorized. Please check the configuration dialog on your device
- waiting for device-

Can someone please provide a quick 1-2 about how to install Android applications using Anbox when ADB is not supported? This is the only thing I saw in the Ubuntu Mobile Docs regarding using adb to install (https://docs.ubports.com/en/latest/userguide/advanceduse/adb.html).

Thank you