The i7-8750H is a supported CPU so I am wondering if you have TPM turned on and if you have TPM 2.0. Also SecureBoot needs to be enabled. Do you get a message describing why it does not meet the specs?
Have 2 Aliens Alienware R3 15 i7-7700HQ and R5 17 i7-8750H Installed with no problem Windows 11 Pro X64 on the i7-770HQ and via Windows Update every driver neededbut while installation of Windows 11 Pro X64 on thw i708750H I'm getting message that machine does not meet the minimum requirements !I'll also try to make an image of the installation on the 7700HQ (with Macrium Reflect) and try to transfer it on the 8750H and I'll let you know about the outcome.
Alienware R3 15 i7-7700HQ & R5 17 i7-8750H