Firefox, which has most of the desktop extensions also working on mobile.
That is on Apple, unfortunately. Every browser on the App Store is a safari engine with whatever browsers skin on top, essentially.
I thought they lost the court battle about that and were told that they had to actually allow other engines, but I haven’t heard anything else since then.
I believe that apple restricted other browser makers to using safari mobile as a base. Not sure if that’s true/changed, but I’m too lazy to look it up. So maybe take that with a helping of salt.
This is true in America. In the EU, Apple was recently forced to allow third-party browsers. But even in the EU, developing those third-party browsers will take time and money.