Several individualized (login) Front-End and differrent (sub)domains on a single managed nextcloud (ionos) - possible?

I have several managed nextclouds running on IONOS for several small NPOs.
For every NPO I have an individual paid contract with 500G or 1T, why I want to use one single managed nextcloud but keep the front-end individualized.
Id organize the rights via group(folders) (no problem, even welcome, that users can see other users)

Every (sub)domain of each NPO should show the user an individualized login-screen
egs., and
should each

  • point to an individualised login-screen (corporate design)
  • be usable as serveradress for syncing with the NC-client etc.
  • Bonus if possible: have an individualised design in nextcloud (egs. colours)

Is there an NC-App enabling this feature and/or with DNS Ressource Records?

Thank you already!