You will find the file labeled similarly to: Red Dead Redemption [01007820196AA000][v65536].nsp (Note: v65536 is the hex code equivalent for version 1.0.3 on many release sites).
This article was accurate as of May 2026. Always check scene release notes for newer patches beyond v1.0.5. red dead redemption switch nsp update
After updating to v1.0.5, ensure the is active. This DLC is often distributed as a separate NSP file (approx 3.2 GB). If the update is installed but you don't see Undead Nightmare on the main menu, you need to find the [DLC].nsp . You will find the file labeled similarly to: