Slackware 14.2-current (jul 2020).
Code:
root@darkstar:/backup_almacen/soft/pychess# gzip -dv glade-3.18.3.tar.xz
gzip: glade-3.18.3.tar.xz: unknown suffix -- ignored
root@darkstar:/backup_almacen/soft/pychess#
What's this? What is more: I had just used gzip to extract the file from another .xz file without any problem!