@erixbzh With Dell there is in the BIOS a few settings like Hyper-Threading, check if that’s enabled, and most important some Dell have [Software] Raid, if it has raid, wipe it, format and make it bootable, check those settings, disable pxe boot, check boot order, sorry but Dell has too many options to pinpoint only one troublemaker, all different per model. Is your model having TPM?
Sometimes it just helps to ‘Load BIOS Defaults’ and go through all settings related like the boot options, raid, cpu.
Hope it helps.