Unfortunately, the T5500 do not support UEFI and secure boot (TPM) is too old. While you can use a UEFI emulator such as Clover and Chameleon, you will have a even greater dealbreaker with the lack of any AVX instructions on your CPUs if Windows 11 decides to use those features before release. Currently, there are simple fixes to get it to boot with older machines, but more than likely Microsoft will patch those out before release. My only suggestion is to wait for the official release and see if any safe patches or fixes will be allow Windows 11 to boot from older machines.
Found this forum while doing research for my T5500,
I have upgraded to runing windows 11 on my system.
Edition Windows 11 Pro
Installed on 11/27/2021
OS build 22000.194
Experience Windows Feature Experience Pack 1000.22000.194.0
Processor Intel(R) Xeon(R) CPU X5680 @ 3.33GHz 3.33 GHz (2 processors)
Installed RAM 144 GB
System type 64-bit operating system, x64-based processor
Pen and touch No pen or touch input is available for this display
Quick guide on how I got Windows 11 on my T5500:
Rufus(iso to usb): https://github.com/pbatard/rufus/releases/download/v3.17/rufus-3.17.exe
Windows Debloter: https://www.christitus.com/debloat-windows-10-2020/
Powershell command to copy/paste:
iex ((New-Object System.Net.WebClient).DownloadString('https://git.io/JJ8R4'))
Windows 11 Unsupported
Step 1: Make a Windows 10 USB Installer with Rufus
Step 2: Open Windows 11 ISO and copy the install.wim “Exp E:\sources\install.wim”
Step 3: Past and replace into the windows 10 sources folder, “Exp F:\sources”
Win 10 Upgrade
Step 4: On the Windows 10 USB got the sources folder and run “\sources\setupprep.exe”
Step 5: IMPORTANT, Select “Change how Windows Setup downloads updates” and chouse “Not right now”
Step 6: Continue the setup process and you will be running windows 11 on your unsupported hardware.