upgrade to macOS monterey could not be completed , it request firmware update i can not find it

A suggested upgrade path from El Capitan through detour High Sierra

could be the travel ticket for weary travelers; along long, winding roads.

• How to get old versions of macOS - Apple Support

https://support.apple.com/en-us/HT211683

Some build model years cannot get to Monterey Turnpike.

They take an exit sooner at Catalina; or coast in at Big Sur.

[Firmware updates - are selectively hidden - within these. ]