Attempting to install on MAC OS 10.14.6 (Mojave) ..
I am getting this popup ?!?

“kdenlive-21.12.3.dmg” can’t be opened
because Apple cannot check it for malicious
software.

This software needs to be updated. Contact
the developer for more information.


Your help is most appreciated

I know nothing about MAC but this could be your antivirus blocking the software, you can disable the antivirus just to test but be sure if it's really the official kdenlive file.
You can also just wait for someone else to answer because as I said, I know nothing about MAC.

Peace

Please follow this steps: https://docs.kdenlive.org/en/getting_st ... e-on-macos