@corlock I found some of my previous experiments at https://github.com/soapdog/h/tree/addon-firefox/h/browser/firefox but this is old-style add-on, not even a webextension. I've looked into the current code on their repo, it changed a lot :-)

This link from MDN contains some pointers on porting from Chrome and this webextension polyfill will help you create add-ons that work on multiple browsers from a single codebase. From their readme file:

This library allows extensions written for the Promise-based WebExtension/BrowserExt API being standardized by the W3 Browser Extensions group to be used without modification in Google Chrome.

If you opt to start the sbot node with native messaging, look into this NPM module that helps with coding/decoding native message interface and if you want the patchfox repository has a host_app folder that contains the companion app, it known native messaging and can show a bit on how to start sbot.