I targeted Chrome for the proof of concept because of its market share, but to be honest, I use and prefer Firefox as my default browser.

Manifest v3 is a remarkably hostile development environment: Google knows that people block advertisements with extensions and want to limit their scope. I had to adapt a lot of code, and as such, making it work cross-browser would require more than a few changes. But I understand your point and want Pinbot to run on more browsers, especially Firefox!