Ways to separate accesses within Jira

[Daria A]

Hello!

I'm looking for a solution on how to split one Jira instance into two or more. I need to make it so that not only some of the users cannot view projects, tasks, but also that there is no physical possibility to add them to a roles of projects and tasks.

For example, fields with the type User picker have a User filtering setting that allows you to limit the list of users in the drop-down list. Is there such a possibility for the Add users to a role button in the Users and roles section of the project?

I assume that something similar can be implemented via Scriptrunner, but so far I don't understand how. Or maybe you've seen a plugin that would help divide Jira into two parts?