There is no legitimate method to install Diablo IV for purely offline use. Even for solo players who prefer to ignore social features, the following requirements remain mandatory:
Some users confuse "Offline Mode" with "Local Co-Op." Diablo IV supports couch co-op on consoles. You can play with two people on one screen without a second console. diablo iv offline mode install
The Steam Deck community has been fighting for an offline mode since launch. As of the latest patches (Season 4 and 5), Diablo IV actually has a pseudo-offline mode for Steam Deck, but it is glitchy. There is no legitimate method to install Diablo
Here is the most efficient way to get Diablo IV running on a PC with limited or mobile hotspot data. diablo iv offline mode install