I have figured this out! I have the answer to all Mac products after 2017... The features is disabled by the T2 security chip. You can lower the level of startup security and then Wifi Spoof will work. I have verified this works! I have spoofed the MAC address for a travel router and an Apple TV and logged into web authentication protected wifi systems... See the below link: https://support.apple.com/en-us/HT208198
Yes, I found that link you cited a day ago and tried it before seeing your post.
Found my file under ~/Library/Containers/com.apple.Safari/Data/Library/Preferences/com.apple.Safari.Extensions.plist.
I dragged that file onto SRExport, but a "SRExport quit unexpectedly" error was returned:
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
went to https://sessions-extension.github.io/Sessions/export.html , downloaded the script and following the instructions attempted to run it. Terminal returned the following error:
ERROR /Users/danielcarlock/Library/Safari/Databases/safari-extension_yoo.david.sessions-deub45nr9t_0/ is either unreadable or contains no databases.