Comment # 32 on bug 1203748 from Stefan Dirsch

I think I never updated the BIOS. 

# fwupdmgr get-updates
WARNING: Firmware can not be updated in legacy BIOS mode
  See https://github.com/fwupd/fwupd/wiki/PluginFlag:legacy-bios for more
information.

So I'm still running either in legacy BIOS or CSM UEFI BIOS in "CSM
compatibility mode". And switching to UEFI would probably mean I would need to
reinstall the whole system. So I guess I need to update the BIOS by other
means. Hope I can still find an update somewhere. Maybe this is then doable by
a USB stick with FreeDOS on it. But first I need to make a backup of my data.