@Marathon2422
I've tried the adaptation from the video several times. I had no luck with it.

@ezze
Of course, we have to be careful when installing files that come from unknown sites. And: It seems to me that all devicesget the same MAC. That does not bother me. I do not do banking with the tablet, I do not mind with google or any "social networks". I would not even look at my e-mails with a tablet.
Anyway, when I flash cool-6, all the modifications are gone. I get back the files "WIFI" and "WIFI_CUSTOM" that do not run.
But:
Maybe someone can work up the facts to the extent that CONTROLLED and SAFE files "WIFI" and "WIFI_CUSTOM" are delivered during the installation process of the ubports-installer. Unfortunately I am not able to do that.
It seems that not only BQ M10 tablets are affected.

How to get rid of the following error message when entering the command line
'sudo apt-get update':
'W: No sandbox user' _apt 'on the system, can not drop privileges'
Is the message a problem at all?

@1896er
The problem is solvable. Please refer to
https://forum.xda-developers.com/showthread.php?t=2730486
At the bottom of the page you will find the text:
Attached Files
Wifi Fix Files.rar - [Click for QR Code] (187 Bytes, 339712 views)
After downloading and unzipping the file Wifi Fix Files.rar you get two files:
WIFI and WIFI_CUSTOM
These two files must be in the folder
/Data/nvram/APCFG/APRDEB
be copied (overwrite the existing files)
In conclusion, do not forget reboot.

Unfortunately my statement of 11 Oct 2019, 16:53 is not the whole truth. LibreOffice and Firefox are running sometimes on libertine (but sometimes not). Unfortunately, it does not always work when I create a new container.
So if necessary, remove the existing container and build a new one. Maybe the following PPAs will help as well:
ppa: ubports-developers / overlay
ppa: ubuntu-touch-core apps-drivers / collection
ppa: libreoffice / ppa
ppa: mozilla team / firefox-next

@Marathon2422
I had done the "repairing by copying 'WIFI' and 'WIFI-CuSTOM' into the path '/data / nvram / APCFG / APRDEB /' " on a fresh installation of "devil" (on 2019-10-20). After changing to "rc" (also 2019-10-20) the Wifi address was unchanged and Wifi was automatically connected.
The problem seems not to be Ubports, but the basic flashing of "cooler" (for BQ_M10_HD) with "SP_Flash_Tool_v5.1824_Linux". I already tested that a few days ago.
Flashing again UBports installer (0.2.7-beta) (at 2019-10-20 to the installation from 2019-10-19) did not change the wifi address. So I had not to repair the WIFI again. My wifi network connected automatically immediately.
Wifi_fix will only be necessary if you switch (comming from Android or original BQ-Ubuntu via) "cooler" to Ubports.

After months of searching, I finally found a solution for the problem - that even I understood.
With some commands in the terminal, the error can be corrected. Please refer to:
https://forum.xda-developers.com/showthread.php?t=2730486
Thanks to Nilendu from India

Using Libertine Firefox 69.0.2 can be used with Libertine.
Using Libertine: LibreOffice can be installed but does not run.
This is true for BQ M10 HD - Ubports 16.04/stable 2019-10-08 and
Fairphone2 - Ubports 16.04/devel 2019-10-11.

@emailforfor At least I tested "Import" / "EXPORT" of bookmarks and unfortunately there is a mistake in my information from 30.09.2019! The bookmarks are stored in "/home/phablet/.local/share/morph-browser/bookmarks.sqlite". Sorry abaut that.

Today there is an easier way to "EXPORT" an "IMPORT" the telephone-book (and the bookmarks).
With FILE MANAGER the file
"/home/phablet/.local/share/evolution/addressbook/system/contacts.db"
can be copied. To install the file on another UT device, first delete the existing file at this path and then copy the database to be imported into the path described above.
I did not test import/export of bookmarks. With the morph-browser you'll find 2 databases in path
"/home/phablet/.local/share/morph-browser/databases/":
"Databases.db" and "Databases.db-jounal"
Remember: reboot is required.