The oldest CPU supported by Windows 11 are very selected late 2017 gen 7 CPU models.
You have a 2015 gen 5 CPU.
- nobody wants to spend the money to fix future Meltdown and Spectre related security vulnerabilities which involved patching BIOS
- computer manufacturers only supplied the new DCH type of drivers (which Microsoft invented to reduce security problems) in 2018 model or newer
You can absolutely install Windows 11 manually on your computer.
But every patch Tuesday of every single month, you would be wondering whether (1) Microsoft will push the monthly update to you which could kill your computer or (2) that Microsoft will blacklist your computer because you have outdated drivers and you would be left out of security updates.