New kid (and mobile model) on the block... - Android Q&A, Help & Troubleshooting

Hello all, I have a little project I'd like some help on. I have recently bought an Alba 4 inch with android 7 (Nougat). I'd like to use this phone purely for SatNav work, but it appears that it doesn't like working the GPS without SIM or wireless. I have done some research and apparently, a few people have experienced a similar issue when updating from android 6 to 7. So I thought I'd root my 'Alba' and flash it back to 6 to see if that improves the GPS usage unless someone can tell me otherwise. It's quite maddening as I have an old Nokia Lumia 925 (Windows 8.1) which has no problem using the internal GPS device without wireless or SIM card - in fact, my old N8 and X6 have no problem at all and I still use those but software is now almost defunct. However, I'd like to pursue with the 'Alba' as I want to install OsmAnd or equivalent app and upload created gpx routes from my laptop, for me to use on my mountain bike or road bike. The reason I'm going for a fairly simple mobile, but should fit the bill, is that it can be charged while out in the wild with a basic solar power pack. My other phone the Honor 8 requires more than a simple solar pack....
Details of phone - Alba 4 3g (AC40AS3G / SKU133814622) with Archos android 7.
Steps taken...
'OneClickRoot' doesn't have a root app entry for my particular phone. Now I've done the build number trick, allowed usb debugging, got the PC authorised on the phone, installed android sdk on my Ubuntu 12.04 laptop and I can run adb and some commands:
'adb devices' creates:
[email protected]:~$ adb devices
List of devices attached
18643080980731 device
'adb shell' creates:
[email protected]:~$ adb shell
ac40as3g:/ $
'adb reboot bootloader' - gives a screen with 'fastboot mode' in the top left corner of the mobile.
'fastboot oem unlock' and 'fastboot flashing unlock- both give "< waiting for any device >" but no listing
'fastboot devices' - this then produces "no permissions (user in plugdev group; are your udev rules wrong?); see [developer website] "
My lsusb command produces this, with phone connected in normal mode:
userATlaptop:~$ lsusb
Bus 002 Device 004: ID 0e79:5604 Archos, Inc.
Bus 008 Device 002: ID 8086:0189 Intel Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
My 51-android.rules file contains :
SUBSYSTEM=="usb", ATTRS{idVendor}=="12d1", MODE="0666", GROUP="plugdev"
SUBSYSTEM=="usb", ATTRS{idVendor}=="0e79", MODE="0666", GROUP="plugdev"
I also have a custom rule called '70-abdroid-custom-device.rules' which I created from some 'googled' page...
# Archos 4
ACTION=="add|change", SUBSYSTEM=="usb", ATTRS{idVendor}=="0e79", ATTRS{idProduct}=="5609", TAG+="uaccess"
ACTION=="add|change", SUBSYSTEM=="usb", ATTRS{idVendor}=="0e79", ATTRS{idProduct}=="5604", TAG+="uaccess"
'fastboot flashing get_unlock_ability' - this produces "< waiting for any device >" but nothing.
So questions are:
Have I got my udev right?
What would be the next step after correcting the first question?
...any other suggestions? Apart from 'throw it in the bin...' thanks.