I checked Dell computers tested for upgrade to Windows 11 shown that XPS 15 9575 was listed in the tested list.
However, when I check using PC Health Check application by windows, it showed that the PC cannot run Windows 11.
Is my model cannot run Windows 11?
My first guess would be that TPM is not enabled in the BIOS. I have a 6 month old self built and at first it came back as not able to run Windows 11. I enabled TPM and all was well.
If so that would almost be contradictory. The system has an 8th generation CPU and is on the Dell list as having successfully tested for Windows 11. I expect that when MS releases the newest version of their health app it may come back as compatible. I would think that possibly UEFI or Secure Boot may be the culprit but everything is so up in the air now that it's best to wait until MS gets the required specs locked down.