Have you tried the Yandex browser? I sawn in multiple posts and sites that Yandex supported the extension in IOS. And if even after trying the yandex you failed to use it maybe there is also need some edits in scripts to use in iPhone.
I don't recommend anyone using Yandex browser.
Last time I checked this russian browser had modified closed source code based on Chromium.
I heard about orion browser for iPhone that works with extensions.