My hardware: MacBook Pro (Retina, 15-inch, Mid 2015) – A1398

In 2018 I research the interface of the Apple-SSD interface, turns out it has NVME capability with tested R/W speed 2000MB/s
So I upgraded the disk to WD NVME-SSD 1Tb Black (WDS100T2X0C) running verry nicely.

Updating MacOS went just fine from ‘Yosemite (10.10)’ and on till ‘Catalina (10.15)’,
I posponed the upgrade after this becouse of the major (IMO) iTunes cluster-F* ripping all the functionalities out and making it even worst then iTunes .. **go figure!
And the significant changes to the interface in Big Sur and Maverick, so delaying the update from 2019..2022.

So after multi-timemachine backups I started the upgrade all looked fine until the reboot.
It was rebooted in to the recovery enviroment and the message “A required firmware update could not be installed.”
Just rebooting with the <option> key pressed and selecting the MacOS-disk reverted back to the old Catalina.

After reading some DuckDuckGo.com* searches it turns out updating the firmware requires an original Apple-SSD.

I could not find the old one, so ordered a 2nd-hand 256Gb Apple-SSD online.
Installed catalina and upgraded to Monterey on the Apple-SDD,
Afterwards replaced the NVME-SSD, booted and upgraded to Monterey smoothly.

My firmware was too old to use an workaround doing it manually.
The Eclecticlight Company Utility SilentKnight nice tool to view the current firmware

*DuckDuckGo.com results:
Monterey: “A required firmware update could not be installed.”
Which firmware should your Mac be using? (version 6)firmware-should-your-mac-be-using-version-6/

Goodluck upgradeing..