I am very new to SharePoint and looking for a way to create a list or library in one team site and then reference that list from another team site. In research thus far I have come across descriptions of ways of achieving this using site collections. However, this appears to go against the modern UI and 'flat world' approach to SharePoint. It would also be preferable to have a solution that is easy to implement for individual users, rather than requiring a site admin.
A common request that might be similar to yours is to create a central repository of Document Templates, Manuals and so forth in one Site Collection and then reuse that repository in each "Customer Case"/Project/Team Site , each of them a new Site Collection. This is very often implemented using search. The search result source is defied on the tenant level and therefor readily available on the new sites. That said, IFAIK Modern UI doesn't have a Search Results web part yet so you have to use a classic page on the site to display any search related stuff :-(