Comment # 1 on bug 1154139 from pgnd _

found the cause of the fail @

    Bug 1512064 - User not authorized for network , power etc 
    https://bugzilla.redhat.com/show_bug.cgi?id=1512064#c3

        "
        It was affected by a lite hardening
        I'm  setup  /proc as different fs with hidepid parameter. After removed
one entry from fstab  and restart problem solved . 

        #proc            /proc           proc    nosuid,nodev,noexec,hidepid=2 
      0       0
        "

on my systems, I've had

    /etc/fstab
        proc     /proc    proc    rw,nosuid,nodev,noexec,relatime,hidepid=2   
0 0

for as long as I can remember; and has been working without issue until
"sometime recently" ...

per,

    http://man7.org/linux/man-pages/man5/proc.5.html
    https://linux-audit.com/linux-system-hardening-adding-hidepid-to-proc/
   
https://www.phoronix.com/forums/forum/phoronix/latest-phoronix-articles/1093763-in-2019-most-linux-distributions-still-aren-t-restricting-dmesg-access/page4


'hidepid=2' is supported hardening for /proc

here, changing

-        proc     /proc    proc    rw,nosuid,nodev,noexec,relatime,hidepid=2   
0 0
+        proc     /proc    proc    rw,nosuid,nodev,noexec,relatime             
0 0

fixes the issue.

after reboot,

    ps ax | grep polkit
         2669 ?        Ssl    0:00 /usr/lib/polkit-1/polkitd --no-debug
         3002 ?        Sl     0:00
/usr/lib64/libexec/polkit-kde-authentication-agent-1

and I can, again, 

    -- mount USB/eSATA attached removable drives
    -- install VirtualBox extension packs
    -- etc

So to get this working, atm requires UN-hardening the /proc mount, by removal
of the "hidepid=2" option.

It's not clear that this is a new/recent requirement for linux FSs, or a bug
that's arisen in distro &/or KDE ...

Something's changed -- the question is what/why?