my pc is also showing "Secure boot unsuported". Is it somehow possible to activate Secure boot and upgrade TMP to 2.0 in following optiplex 790?. will optiplex 790 recieve any Updates with regard to Bios from Dell?.  Many users can still install windows 11 on it and it is working fine. 

Machine Dell Inc. - OptiPlex 790
Operating System Microsoft Windows 10 Pro (64-bit)
Memory 8 GB
Processor Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz
Motherboard Dell Inc. - 0HY9JP
Video Cards Intel(R) HD Graphics
Monitors DELL P2217H
Hard Disk HP Photosmart Wirel USB Device (0 Bytes)
Network Card WAN Miniport (IKEv2)

TPM: 1.2 version 8.28