A combination of a few things. It is all in the PDF at WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free with the screenshots
In short:
- verified that the SATA mode selection was AHCI (make sure the SSD can be found)
- power settings advanced / sleep type support is Legacy S3 standby (the default new Windows UEFI settings sometimes conflict with Linux AND this will allow you to click on the legacy boot mode later on)
- secure boot is disabled (to allow non signed Linux images to boot)
- save the BIOS setting and power off (for 10 sec according to 1 foru0
- in boot priority/legacy boot; enabled
- Mark Boot USB devices first (in case reboots from the flash image is needed)
- save settings
- power off
- plug in USB stick
- power on with the boot selection menu in the UEFI
- select the USB stick