Injecting javascript into website before it get's to the end user (mobile phone)

[weidah]

In my small business we use online services which are great, but lack some things when it comes to cross service communication.
I've written some Javascript that handles this and it works great. We've been using this for the better part of the year.
We're using Scripty or other JS injection extension for chrome.


For a long time I've been thinking about how to get this onto mobile phones, that don't support these extensions.
Is there a suggested way to do this? We only need to get the Javascript injected on ios/ipadOS/Android devices.

Proxy maybe? Is there a suggested one for OPNsense or a different way someone would go about at getting this to work?


Best regards,

Tom