> any guidance on how we can remove that restriction in code.
This is a limitation implemented in the app, so the only way to remove this restriction is to have a subscription if your students are using the official Moodle app.
The other option is to have a Branded app, either contracting Moodle services at moodle.com/branded-app or compiling it yourself from github.com/moodlehq/moodleapp. Please note that the core team doesn't have the resources to assist you on compiling your own. You can get some guidance by reading the documentation and anyone else is welcome to help.