while running beta client (because I was hoping this would maybe solve the issue that I cannot use a btrfs-on-ssd based library folder - which it didn't) all of a sudden (couple weeks ago now) the client stopped working.
It just wouldn't load.

here's the issue:

[lieven@localhost ~]$ steam
Running Steam on mageia 5 64-bit
STEAM_RUNTIME is enabled automatically
/home/lieven/.local/share/Steam/steam.sh: line 756:  9903 Illegal instruction     $STEAM_DEBUGGER "$STEAMROOT/$STEAMEXEPATH" "$@"

I did manage to solve it by returning to the standard client instead of beta.

• removed the "beta" file from "package" folder in user homedir
• ran steam --reset
• started steam again logging in with account and starting from scratch

found the instructions for this here

Is there a reason why beta cannot be used anymore?

some system info:

[root@localhost ~]# cat /etc/issue
Mageia release 5 (Official) for x86_64
Kernel 4.1.8-desktop-1.mga5 on a 4-processor x86_64 / \l

[root@localhost ~]# cat /etc/redhat-release 
Mageia release 5 (Official) for x86_64

[root@localhost ~]# uname -a
Linux localhost 4.1.8-desktop-1.mga5 #1 SMP Sun Sep 20 12:39:07 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux