Comment 6 for bug 1603815

Strangely enough, no issue on Fedora 27 or Debian 9 Jessie nor Debian 10 Buster.
Really strange, considering Ubuntu 18.04 is based on Debian 10 !!!

After comparing many files, it appears that the 2 last files of /etc/NetworkManager/NetworkManager.conf have been added on Ubuntu !

Debian 10:
    cat /NetworkManager/NetworkManager.conf
    [main]
    plugins=ifupdown,keyfile

    [ifupdown]
    managed=false

Ubuntu 18.04:
cat /etc/NetworkManager/NetworkManager.conf
    [main]
    plugins=ifupdown,keyfile

    [ifupdown]
    managed=false

    [device]
    wifi.scan-rand-mac-address=no

I removed this 2 files, and now Wifi works perfectly. The wifi passphrase is accepted, and even going to sleep mode and back is fine.

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I would strongly recommend to modify /etc/NetworkManager/NetworkManager in package network-manager to remove the 2 last lines. In fact this file should not be modified by Ubuntu and kept as in Debian.
Is it possible to do it in Ubuntu before 18.04 LTS to be launched ???
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It seems this 2 lines have been added due to bug 1681513:
https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1681513
As reported here:
https://askubuntu.com/questions/905283/wifi-issue-with-ubuntu-17-04

By the way, file NetworkManager.conf is empty in Fedora.

Cheers
Fred