It looks like with macOS Big Sur releasing tomorrow it's giving Safari the ability to use Firefox / Chrome with little to no code changes:
"Apple is shipping an extension converter to let you port your extension (from Firefox to Safari) quickly. When you run it, it’ll tell you if everything is going to work as expected. You can then package it in an Xcode project, sign it and submit it to the App Store."
I love the concept of LocalCDN, but I use Safari - do you see this as a possibility for you? If not, when I get a dev cert, I'll see if I can just one-click convert it and publish it on Safari! ☺️