Skypeforlinux won't launch anymore

I experienced the same issue after upgrading under Centos 7 to version from

I found by examining the logfile, the following messsage:] The SUID sandbox helper binary was found, 
but is not configured correctly. Rather than run without sandboxing I'm aborting now. 
You need to make sure that /usr/share/skypeforlinux/chrome-sandbox is owned by root 
and has mode 4755

If you follow the instructions in the error message:

    chmod 4755 /usr/share/skypeforlinux/chrome-sandbox

it fixes the issue.

So, your skypeforlinux version is, the current up-to-date version at this moment - which was released fairly recently. In fact, I have the exact same version on my Debian 10 system, and it works just fine.

The int3 is a x86 processor instruction that is used to implement debugging breakpoints.

But in your case, the int3 is encountered while skypeforlinux is not being run under a debugger, so the int3 trap vector points to a default kernel routine, which is essentially equivalent to sending a SIGTRAP signal to the program.

Why does the skypeforlinux program code include int3 instructions in a production version with no debugger present? Only the people at Microsoft with access to the source code of skypeforlinux could answer that without a significant reverse-engineering effort.

Note that Microsoft only promises that skypeforlinux will work on Ubuntu, Debian, OpenSuSE and Fedora. It could be that this most recent version may have accidentally included some debugging code that only gets executed when some condition does not match any of the supported distributions - and causes Skype to crash because the expected debugging environment is not present.

You could try downgrading Skype to the previous version (or any of the versions listed in the apt-cache policy output) and seeing if that works better for you:

# apt install skypeforlinux=
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be DOWNGRADED:
0 upgraded, 0 newly installed, 1 downgraded, 0 to remove and 0 not upgraded.
Need to get 0 B/79.0 MB of archives.
After this operation, 1,024 B of additional disk space will be used.
Do you want to continue? [Y/n]

If downgrading the package version helps, you might want to set the package on hold, so apt upgrade won't upgrade it again until you remove the hold:

# apt-mark hold skypeforlinux

You might then send a bug report on your experiences to Microsoft, but since they don't make any promises to support Kali, it might get ignored or assigned a very low priority.

I had this issue in Manjaro. After researching it, I found that

chmod 4755 /usr/share/skypeforlinux/chrome-sandbox

is not the preferred method for resolving the problem in Arch or Debian-based distros. Instead, it's suggested to use

sudo sh -c 'echo "kernel.unprivileged_userns_clone=1" > /etc/sysctl.d/00-local-userns.conf'

for a persistant solution. More info can be found at the LXC-Debian Wiki.

EDITED: Jonas Berlin points out a broken command in the original and further checking verifies his comment. Also, removed previous link to the incorrect command. Thanks, Jonas.