Use the Mac operating system that came with your Mac

Please refer to the posting from @John Galt before moving forwards.

This method will WIPE ALL Data and there is No DATA Recovery - Period.

>> Only works on Intel Based Apple Computer <<

To perform this action will require booting from a Bootable Installer. 

The Bootable Installer can Only be performed on an Apple Computer 

This will have to be performed from a Qualifying Computer to run the version of macOS to be made on the Bootable Installer.

Example : Bootable Installer of Mojave would have to be done on a computer that Qualifies to run Mojave.

Notation: If the computer being used to perform this action is Too New or Too Old to qualify to run the version of macOS - this computer can not be used.

Alternative is, to gain access to a Qualifying Apple Computer from a family member, friend or associate.

Extra Special Notation regarding the Touch ID equipped Apple Computer.

 About Startup Security Utility and Must Enable from Recovery Mode the ability to boot from External Drive Before Attempting 

1 - Shutdown computer and disconnect all external drive Except the newly created Bootable Installer.

2- Restart and immediately hold the OPTION key until the Startup Manager appears and choose the USB Drive. 

3 - It will present options >> Disk Utilities >> View >> View ALL attached Drives. 

4 - Choose the Upper Most Drive ( not the volumes indented and list below ).

5 - The drive normally is called Apple Media or Apple SSD - that is the drive to Erase and format as APFS with the GUID Partition Map. This applies to macOS 10.14 Mojave and above. 

6 - Once that is done >> backup out of Disk Utilities and choose install macOS. 

7 - Follow the prompts and it may automatically reboot several time. 

8 - Upon a final reboot - Setup Assist will present with the newer version of mac

ku4hx wrote:

My opinion is it's going to be a lot simpler, and "safer" perhaps to just upgrade your app to meet Monterey's requirements.

Agreed. Whatever the limitation happens to be, you are likely to find help adapting your app for Monterey (and ideally later macOS versions) on the Apple Developer Forums.

Use the Mac operating system that came with your Mac, or a compatible newer version - Apple Support (Archived)

"Downgrading" macOS has always been a challenge, and may no longer be possible on newer Macs. I am not sure where your 2016 MBP falls within that limitation, but the essential requirement will be to completely erase the affected Mac. I mention that only so you can appreciate what you will be getting into.

Given recent reports a number of experienced contributors to this site have concluded certain older macOS versions may no longer be available through any means whatsoever. Please understand the implications of that statement. The good news is that — so far — Mojave does not appear to have been affected.

Needless to say you will want to create a backup, and preferably more than just one backup. Then, bear in mind anything created with a newer macOS version may not be readable by an older macOS version. That includes files, documents, Time Machine backups... anything.

Consider all that information seriously before contemplating erasing your Mac.

My opinion is it's going to be a lot simpler, and "safer" perhaps to just upgrade your app to meet Monterey's requirements.

Welcome and thank you too