I am trying to setup multi-site on Drupal 9.1 using a shared codebase with separate databases. Working within each site separately has been fine, and I'm ready to start working on sharing users and content between the different sites. I'd like users to be shared between the different sites, and for content I would like to be able have links between related pages on each (ex: a translated piece on one site links back to the raw scans on another site, and vice versa), though I anticipate I would be coding some sort of shared database/table for my content linking needs. I have been able to find how to perform this in Drupal 7, but not so much 8 and 9. The closest I have seen is the Domain Access module, however that appears to have been made where all the sites are sharing a single database and not separate. Is there a known way to set this up in Drupal 9?