If you have hostonly="yes" in your /etc/dracut.conf.d/50-mageia.conf you need to add the following line manually in order to make suspend to disk/ hibernation work:
add_dracutmodules=" resume "

  Otherwise it will hibernate but then lose the full machine state at boot by booting as if the machine had not ever been hibernated.
  For a generic initrd (hostonly="no") it works out of the box, but this was not the default when installing Mageia 8. The resume module should be included automatically, no matter what the configuration of hostonly is.