Crash Bandicoot 4: It's About Time

A fully offline platformer Platinum with no online trophies.

PS5 Fully offline Platinum

Reason

There are zero online trophies on the base list, and the game does not require a persistent internet connection or server checks to earn any of its rewards.

Local Multiplayer Trophies Can Be Done Offline: A few trophies require local couch multiplayer modes, but these do not require an internet connection, PlayStation Plus, or a second player:
“Fleet of Feet”: Play a game of Checkpoint Race (under Bandicoot Battle on the main menu). You can set the mode to 2 players offline and simply use a single controller for both turns.
“Settle the Score”: Play a game of Crate Combo in Bandicoot Battle using the same single-controller method.
“No It’s MY Turn”: Complete any single level with the Pass N. Play co-op mode toggled on in the pause menu.
Purely Single-Player Grind: The remaining trophies focus entirely on single-player completion, including collecting all 38 Platinum Time Trial Relics (“Faster Than Sound”), all N.Sanely Perfect Relics (“Perfectionist”), and achieving 106% game completion (“OVER-Overachiever”).

(Note: While completely doable offline, this is notoriously one of the hardest platforming Platinums ever created, requiring extreme precision and execution across time trials and deathless runs.)