Latest mac OS that allows unknown developers
I've been stuck on sequoia because I want to continue manually allowing unknown developers. What is the most recent mac OS that will allow me to continue doing this via privacy and security.
It can still be done in Tahoe, although not recommended for the obvious reasons.
Open a Mac app from an unknown developer - Apple Support
This is specific to opening an app, so a System Extension may not work if that developer has not updated it to be compatible with Tahoe. That would be something only the developer could do and they should be able to tell you if it is compatible with Tahoe.