Apple puts the maximum RAM of its new 27-inch iMac at 64GB. However, the memory kit-maker OWC has confirmed that the PC is indeed compatible with twice this value. Therefore, it now sells upgrade kits for this PC that may allow a user to add 120GB of RAM to an iMac base model.
https://www.notebookcheck.net/The-27-inch-iMac-2019-s-RAM-may-be-upgraded-to-128GB.415321.0.html